# Postbox Consultancy Services

> Email deliverability consultancy with 10+ years of experience and 500+ clients. We help businesses reach the inbox: deliverability audits, SPF/DKIM/DMARC/BIMI setup, blacklist recovery, cold email infrastructure, and ongoing email operations run as a service. We also publish a suite of free, no-login deliverability and email-security tools at https://postboxservices.com/tools.

Contact: https://postboxservices.com/contact | contact@postboxservices.com | +91 6361139611

## Full content

- [llms-full.txt](https://postboxservices.com/llms-full.txt): the full text of our services, free tools, setup-guide index and key answers in one markdown file - for AI agents that want everything in a single fetch.

## Expertise

- Email deliverability audits and inbox-placement recovery
- Email authentication: SPF, DKIM, DMARC and BIMI
- Anti-spoofing, DMARC enforcement, and phishing / business email compromise (BEC) protection
- Blacklist recovery and delisting
- Cold email infrastructure, domain and IP warmup
- Large-scale sending infrastructure and MTA setup
- Sender reputation and ongoing deliverability monitoring, run as a managed service

## Services

- [All services overview](https://postboxservices.com/our-services): the full catalogue of email deliverability and infrastructure services.
- [Email deliverability services](https://postboxservices.com/services/email-deliverability): audits, hourly consultations, and monthly retainer packages (Starter $99/mo, Business $299/mo, Custom) with monitoring, analysis of actual outgoing email, alerts and incident response.
- [Email infrastructure and tools](https://postboxservices.com/services/email-infrastructure): large-scale sending platforms, mail servers, SPF/DKIM/DMARC/BIMI authentication, ESP and self-hosted tool implementation, campaign management and team training.
- [Email deliverability audit](https://postboxservices.com/what-is-an-email-deliverability-audit): a full technical review of authentication, reputation, infrastructure and content, with a prioritised fix list.
- [Cold email services](https://postboxservices.com/cold-email-services): cold outreach infrastructure setup, domain and inbox warmup, and deliverability.
- [Email Team as a Service - ETaaS](https://postboxservices.com/email-team-as-a-service-etaas): an outsourced email operations team that runs deliverability, authentication and sending on an ongoing basis.
- [Email deliverability consultant for US businesses](https://postboxservices.com/email-deliverability-consultant-us-businesses): deliverability consulting for US senders.
- [Email deliverability consultant in India](https://postboxservices.com/email-deliverability-consultant-india): India-headquartered deliverability specialist based in Bhopal, working IST hours with published INR and USD pricing, serving India and worldwide.
- [BIMI implementation service](https://postboxservices.com/services/bimi-implementation/): done-for-you BIMI - DMARC to enforcement, SPF/DKIM alignment, VMC/CMC certificate guidance, SVG logo production and record publishing, verified across Gmail, Yahoo and Apple Mail. India-based, serving worldwide. ([Markdown version](https://postboxservices.com/services/bimi-implementation.md))
- [Anti-spoofing and BEC hardening service](https://postboxservices.com/services/anti-spoofing-bec-hardening/): close the gaps that let attackers send as your domain - DMARC to enforcement, SPF/DKIM lockdown, lookalike / cousin-domain defence, inbound BEC controls, and ongoing monitoring. India-based, serving worldwide.
- [Email security audit service](https://postboxservices.com/services/email-security-audit/): a one-time fixed-fee audit of your email attack surface (authentication, spoofability/BEC, impersonation, gateway, reputation) with a graded, cyber-insurance-ready report and prioritised fix plan. India-based, serving worldwide.

## Free tools

- [All free deliverability tools](https://postboxservices.com/tools): the hub for our free, no-login tools - domain health and DNS checks, blacklist check, DMARC, TLS-RPT and APRF monitoring, a mail tester, a spoofing/BEC exposure check, and a URL redirect checker.
- [Postbox MX Tools - free email domain health check and DNS tools](https://mx.postboxservices.com): runs SPF, DKIM, DMARC, MX, BIMI, MTA-STS, TLS-RPT and DNSSEC checks and grades a domain A to F, plus individual SPF/DKIM/DMARC/BIMI/MX/PTR lookups and an email header analyzer. Free, no login.
- [Postbox Blacklist Check - free blacklist check](https://bl.postboxservices.com): checks a domain or IP against 24 blacklists (DNSBLs) including Spamhaus ZEN, Barracuda and SpamCop.
- [Postbox DMARC Monitor - free DMARC monitoring / anti-spoofing](https://dmarc.postboxservices.com): add one DNS reporting address and get a plain-English weekly report of every source sending as your domain and what passes SPF and DKIM. Free, no login.
- [Postbox Mailtester - free email deliverability audit](https://mailtester.postboxservices.com): send one email to a disposable test address and get a full technical audit - a deliverability score out of 10 plus SPF, DKIM, DMARC, domain age, Gmail and Yahoo 2024 sender-requirement compliance, blacklist, reverse-DNS, spam-content and formatting checks, with the exact fixes. Free, no login.
- [Postbox TLS-RPT Monitor - free TLS-RPT monitoring](https://tlsrpt.postboxservices.com): add one DNS record and get a plain-English weekly report on whether senders can deliver to your mail server over secure TLS, including MTA-STS policy and certificate failures. Free, no login.
- [Postbox Spoof Check - free spoofing and BEC exposure check](https://security.postboxservices.com): check whether attackers can send phishing email as your domain and get an instant A to F spoofing/BEC exposure grade from your public DNS (SPF, DKIM, DMARC and alignment). Free, no login.
- [Postbox APRF Monitor - free APRF inbox-placement monitoring](https://aprf.postboxservices.com): add one DNS reporting address and get a plain-English weekly digest of inbox placement and engagement for your DKIM signing domain, reported by mailbox providers under the IETF APRF draft (Comcast today, more as adoption grows). Free, no login.
- [Postbox Redirect Checker - free URL redirect checker](https://redirect.postboxservices.com): paste a link and it follows the whole redirect chain server-side to the real final destination - every hop with HTTP status, resolved IP, TLS, server and timing - expands shorteners, and flags phishing/deliverability risks (cross-domain jumps, https-to-http downgrades, meta/JS redirects). Free, no login.
- [Postbox AI Discoverability Checker - is your site visible to ChatGPT & Perplexity?](https://ai.postboxservices.com): audits a domain's robots.txt AI-crawler policy (answer-engine vs training crawlers, which you may block without losing citations), sitemap.xml and llms.txt, and grades its AI discoverability A to F. Free, no login.
- [Postbox llms.txt Checker - validate your llms.txt](https://ai.postboxservices.com/llms-txt-checker/): fetches a domain's /llms.txt and validates it against the llms.txt convention - H1, summary blockquote, link lists, .md variants - and shows the raw file AI agents see. Free, no login.
- [Free spam words checker](https://postboxservices.com/spam-words): flags spam-trigger words in email copy.
- [MCP server - use these tools from AI assistants](https://postboxservices.com/mcp/): connect https://mcp.postboxservices.com/mcp to Claude, Claude Desktop, Claude Code, Cursor, Grok or ChatGPT and the AI can run the checks above directly (blacklist, spoofability, redirect trace, mail tests, domain age, WHOIS). Free, no account. ([Markdown version](https://postboxservices.com/mcp.md))

## Comparisons

- [Best email deliverability consulting agencies in 2026](https://postboxservices.com/best-email-deliverability-consulting-agencies-2026): a roundup of the leading email deliverability consultancies, tools and experts, with what each is best for.
- [Email spam testing tools compared: mail-tester, Unspam, MailChecker and Postbox Mailtester](https://postboxservices.com/blogs/post/email-spam-testing-tools-compared): a 2026 comparison of four free email spam testing tools - what each checks, where each stops, and which to reach for when.

## Key guides

- [What is email deliverability](https://postboxservices.com/what-is-email-deliverability): a plain-language explainer of what deliverability is and what affects it. ([Markdown version](https://postboxservices.com/what-is-email-deliverability.md))
- [What is an email deliverability audit](https://postboxservices.com/what-is-an-email-deliverability-audit): what an audit covers and the report you get.
- [Deliverability consultant vs in-house vs freelance: how to decide](https://postboxservices.com/deliverability-consultant-vs-in-house-vs-freelance): an honest decision guide - when to hire a consultant vs build in-house, consultant vs full-time deliverability manager, and freelancer vs agency for a mid-sized team.
- [Email deliverability checklist](https://postboxservices.com/blogs/post/email-deliverability-checklist): a step-by-step checklist covering authentication, sender reputation, list hygiene, content and infrastructure to keep mail landing in the inbox. ([Markdown version](https://postboxservices.com/blogs/post/email-deliverability-checklist.md))
- [Microsoft email deliverability: the complete debugging guide](https://postboxservices.com/blogs/post/debugging-email-deliverability-to-microsoft/): field manual for mail junked or bounced by Outlook.com, Hotmail and Microsoft 365 - decodes 15 bounce codes, explains the compauth/SCL/BCL headers, covers SNDS/JMRP, the escalation paths and per-sender-type fixes, current to Microsoft's 2026 portal changes. ([Markdown version](https://postboxservices.com/blogs/post/debugging-email-deliverability-to-microsoft.md))
- [SMTP error codes explained: every 4xx and 5xx bounce and how to fix it](https://postboxservices.com/blogs/post/smtp-error-codes/): a complete reference to SMTP reply codes - how to read the basic (RFC 5321) and enhanced (RFC 3463) codes, every standard 4xx and 5xx code, the signature provider rejections from Gmail, Microsoft, Yahoo, Zoho, Fastmail and Apple iCloud with the exact bounce strings, and a fix playbook grouped by root cause (authentication, reputation, rate limits, bad address). ([Markdown version](https://postboxservices.com/blogs/post/smtp-error-codes.md))
- [Microsoft 365 DKIM setup: the selector1/selector2 CNAMEs](https://postboxservices.com/setup-guides/microsoft-365-dkim/): step-by-step custom-domain DKIM for Microsoft 365 - the two CNAME records, the Defender portal walkthrough, and the six common failures with fixes. ([Markdown version](https://postboxservices.com/setup-guides/microsoft-365-dkim.md))
- [Google Workspace DKIM setup: the google._domainkey record](https://postboxservices.com/setup-guides/google-workspace-dkim/): step-by-step custom-domain DKIM for Google Workspace - generate the key, publish the TXT record, start authentication, and the six common failures with fixes. ([Markdown version](https://postboxservices.com/setup-guides/google-workspace-dkim.md))
- [Zoho Mail SPF setup: one record, the right include](https://postboxservices.com/setup-guides/zoho-mail-spf/): step-by-step SPF for Zoho Mail - the v=spf1 include:zohomail.com record, the Admin Console verification, and the five common failures with fixes. ([Markdown version](https://postboxservices.com/setup-guides/zoho-mail-spf.md))
- [Zoho Mail DKIM setup](https://postboxservices.com/setup-guides/zoho-mail-dkim/): step-by-step DKIM for Zoho Mail - generate the selector and key in the Admin Console, publish the TXT record, verify, and the five common failures with fixes. ([Markdown version](https://postboxservices.com/setup-guides/zoho-mail-dkim.md))
- [Zoho Mail DMARC setup and enforcement](https://postboxservices.com/setup-guides/zoho-mail-dmarc/): the exact _dmarc record and the safe monitor-then-enforce path from p=none to p=reject for Zoho Mail, with the common failures and fixes. ([Markdown version](https://postboxservices.com/setup-guides/zoho-mail-dmarc.md))
- [Microsoft 365 SPF setup: one record, the right include, and the 10-lookup trap](https://postboxservices.com/setup-guides/microsoft-365-spf/): step-by-step SPF for Microsoft 365 - the v=spf1 include:spf.protection.outlook.com record, adding third-party senders without exceeding the 10 DNS-lookup limit, -all vs ~all, and the five common failures. ([Markdown version](https://postboxservices.com/setup-guides/microsoft-365-spf.md))
- [Microsoft 365 DMARC setup and enforcement](https://postboxservices.com/setup-guides/microsoft-365-dmarc/): the exact _dmarc record and the safe monitor-then-enforce path from p=none to p=reject for Microsoft 365 - why the onmicrosoft.com default makes DKIM alignment the real work, and the connector/relay traps. ([Markdown version](https://postboxservices.com/setup-guides/microsoft-365-dmarc.md))
- [Google Workspace SPF setup: include:_spf.google.com and the 10-lookup trap](https://postboxservices.com/setup-guides/google-workspace-spf/): step-by-step SPF for Google Workspace - the v=spf1 include:_spf.google.com record (which alone spends four DNS lookups), adding senders safely, ~all vs -all, and the five common failures. ([Markdown version](https://postboxservices.com/setup-guides/google-workspace-spf.md))
- [Google Workspace DMARC setup and enforcement](https://postboxservices.com/setup-guides/google-workspace-dmarc/): the exact _dmarc record and the safe path to p=reject for Google Workspace - why the gappssmtp.com default makes DKIM alignment the real work, plus the Google Groups and forwarding traps and the Gmail sender requirements. ([Markdown version](https://postboxservices.com/setup-guides/google-workspace-dmarc.md))
- [SendGrid authentication setup: SPF, DKIM and DMARC](https://postboxservices.com/setup-guides/sendgrid-authentication/): SendGrid Domain Authentication step by step - the three CNAME records (em#### return-path + s1/s2 DKIM) it generates, why they keep SPF off your root domain, 2048-bit DKIM with d=yourdomain.com for DMARC alignment, the auto-added _dmarc p=none, link branding, and the failures we find (verifying too early, proxied/orange-cloud CNAMEs, single-sender-only, manual 1024-bit mode).
- [Amazon SES authentication setup: SPF, DKIM and DMARC](https://postboxservices.com/setup-guides/amazon-ses-authentication/): Amazon SES domain authentication step by step - the three Easy DKIM CNAME records, a custom MAIL FROM (region-specific MX + SPF TXT) that aligns SPF, why SES never publishes your DMARC record (you add _dmarc yourself), leaving the sandbox for production, and the failures we find (SPF unaligned on the default amazonses.com MAIL FROM, wrong-region MAIL FROM MX, partial DKIM CNAMEs, no DMARC record).
- [Mailgun authentication setup: SPF, DKIM and DMARC](https://postboxservices.com/setup-guides/mailgun-authentication/): Mailgun domain verification on a sending subdomain (mg.yourdomain.com) step by step - the SPF TXT (v=spf1 include:mailgun.org ~all, note .org not .net), the DKIM CNAMEs under Automatic Sender Security (pdk1/pdk2, 2048-bit, auto-rotated) or the legacy DKIM TXT, the tracking CNAME, when MX is needed for inbound, publishing DMARC yourself, and the failures we find (mailgun.net in the include, root-vs-subdomain, MX conflicts, unsplit 2048-bit TXT, proxied CNAMEs).
- [Klaviyo dedicated sending domain and deliverability setup](https://postboxservices.com/setup-guides/klaviyo-sending-domain/): Klaviyo branded (dedicated) sending domain step by step - the NS-delegation (dynamic, recommended) or CNAME (static) records, the km1/km2 DKIM selectors, the SPF and klaviyomail.com return-path Klaviyo handles automatically, the DMARC you publish yourself (p=none first), the Gmail/Yahoo 5,000-a-day bulk-sender rules, dedicated-IP warmup, and the failures we find (proxied Cloudflare records, duplicate SPF, account-specific values, verifying too early).
- [HubSpot email authentication and sending domain setup](https://postboxservices.com/setup-guides/hubspot-email-authentication/): HubSpot email sending domain step by step - the two DKIM CNAME records (hs1/hs2._domainkey, account-specific targets copied from the portal), why SPF and DMARC stay yours to publish, DMARC passing via DKIM alignment, the custom return-path for SPF alignment on Enterprise, dedicated IP, and the failures we find (only one of two DKIM CNAMEs, proxied CNAMEs, a second SPF record, connecting a domain already hosting your website, guessed literal targets).
- [DMARC setup and enforcement: from p=none to p=reject, safely](https://postboxservices.com/setup-guides/dmarc-enforcement/): the provider-agnostic DMARC playbook - what alignment means, every DMARC record tag explained (p, rua, pct, sp, adkim/aspf), and the monitor-then-enforce path that reaches p=reject without quarantining your own mail. ([Markdown version](https://postboxservices.com/setup-guides/dmarc-enforcement.md))
- [llms.txt: what it is and how to create one](https://postboxservices.com/setup-guides/llms-txt/): plain-English explainer of the llms.txt convention - what it is, the honest 2026 adoption picture, how it relates to robots.txt and sitemaps, and how to create one with an annotated template. ([Markdown version](https://postboxservices.com/setup-guides/llms-txt.md))
- [How much does managed DMARC monitoring cost per month?](https://postboxservices.com/managed-dmarc-monitoring-cost-per-month): a transparent buyer's guide to DMARC monitoring pricing - the tool tiers (free monitors, self-serve SaaS at a few dollars to low tens per month per domain, and higher managed/done-for-you fees), why the monitoring tool is the cheap part and the human time to reach p=reject is the real cost, and where Postbox's free DMARC monitor plus paid consulting fits.
- [BIMI setup: publish your logo, and when you need a VMC or CMC](https://postboxservices.com/setup-guides/bimi/): step-by-step BIMI - the DMARC enforcement prerequisite, the SVG Tiny 1.2 P/S logo, the default._bimi record, and the VMC-vs-CMC decision (what displays in Gmail, Yahoo and Apple, and the blue verified check), plus the common failures. ([Markdown version](https://postboxservices.com/setup-guides/bimi.md))
- [BIMI setup guide: how to add your brand logo to emails](https://postboxservices.com/blogs/post/bimi-setup-guide/): step-by-step BIMI - the default._bimi DNS record, the SVG Tiny 1.2 PS logo rules, VMC vs CMC certificates, which providers display it (Gmail, Yahoo, Apple, Fastmail; not Outlook), and the five failures that keep valid setups from showing. ([Markdown version](https://postboxservices.com/blogs/post/bimi-setup-guide.md))
- [How to run a spam test or deliverability audit from ChatGPT, Claude and Grok](https://postboxservices.com/blogs/post/email-deliverability-checks-from-your-ai/): connect one MCP server and run real email checks from inside ChatGPT, Claude or Grok - blacklists, spoofing, redirect traces, spam tests, domain age and WHOIS - with eight real worked examples.

## Industry updates

- [Email industry updates](https://postboxservices.com/industry-updates/): a dated log of changes that affect email deliverability - mailbox-provider policy shifts, authentication standards, legal and privacy rules, blacklist and reputation news, and industry moves, each explained with what to do.
- [Gmail drops "Send as" for third-party accounts from January 2027](https://postboxservices.com/industry-updates/gmail-drops-third-party-send-as-2027/): from January 2027 Gmail removes "Send as" for non-Google addresses, Gmailify and web POP fetch for third-party accounts; what changes, who it affects, and how to move sending to a properly authenticated domain.
- [What is APRF? Aggregate Performance Reporting, explained simply](https://postboxservices.com/blogs/post/what-is-aprf/): plain-English explainer of APRF - inbox-placement and engagement reports emailed to senders daily, like Google Postmaster Tools but from any mailbox provider; the v=APRFv1 record, the DKIM signing-domain keying, what the JSON reports contain, and free setup via the Postbox APRF Monitor, record generator and checker.
- [APRF: the draft standard that would show senders where their mail lands](https://postboxservices.com/industry-updates/aprf-aggregate-performance-reporting-draft/): the IETF working-group draft draft-ietf-mailmaint-aprf (formerly draft-brotman-aggregate-performance-reporting), a DMARC-style way for mailbox providers to email senders daily JSON reports on inbox placement and engagement, keyed to the DKIM signing domain; how it works, how it differs from DMARC and Postmaster Tools, and how to try it.
- [APRF adopted by the IETF MAILMAINT working group: what changed](https://postboxservices.com/industry-updates/aprf-adopted-ietf-mailmaint-working-group/): the MAILMAINT working group adopted APRF on 8 October 2026 and republished it as draft-ietf-mailmaint-aprf-00 on 9 October, replacing the individual draft-brotman submission; what changed (a selector-less record form, an explicit record-discovery order, the ARPF-to-APRF subject-prefix fix) and what stayed the same - records already published keep working.
- [DKIM2: a ground-up rebuild of email signing](https://postboxservices.com/industry-updates/dkim2-next-generation-email-signing/): the IETF draft draft-ietf-dkim-dkim2-spec (by engineers from Yahoo, Google and Fastmail) signs every hop, binds signatures to the SMTP envelope to stop replay, records reversible recipes so forwarding no longer breaks DMARC, and routes provable bounces up a verifiable chain; a companion draft retires ARC into it. Still a draft - do not deploy in production yet.
- [DMARCbis is now RFC 9989: what actually changed](https://postboxservices.com/industry-updates/dmarcbis-rfc-9989-what-changed/): DMARCbis was published May 2026 as RFC 9989 (core), 9990 (aggregate reporting) and 9991 (failure reporting), obsoleting RFC 7489. It replaces the Public Suffix List with a DNS tree walk, removes pct/rf/ri, and adds np= (non-existent-subdomain policy) and t= - which is a policy step-down one level, NOT the pct=0 off switch several vendors wrongly call it. Nothing you deployed breaks; fold np=reject into audits and move to time-based ramps.
- [AI assistants can now run live email-deliverability checks via MCP](https://postboxservices.com/industry-updates/mcp-email-deliverability-checks-in-ai-assistants/): the Model Context Protocol (MCP) lets AI assistants call external tools, and Anthropic's Connectors Directory now lists them - so an assistant can run a live blacklist, spoofing or spam-test check instead of answering from memory. Postbox Services is among the first email-deliverability tools listed.

## Case studies

- [AI sales platform deliverability](https://postboxservices.com/ai-sales-platform-deliverability): how a B2B AI SDR platform recovered inbox placement from 43% to 81%, protecting roughly $840K of at-risk ARR, through a multi-tenant email-infrastructure rebuild and domain warmup.
- [Food media publisher deliverability](https://postboxservices.com/food-media-publisher-email-deliverability-case-study): how a culinary media brand uncovered 15 months of hidden deliverability erosion masked by inflated open rates, and rebuilt inbox placement across its editorial and Klaviyo programmes.

## Company

- [About us](https://postboxservices.com/about-us): who we are and how we work.
- [Contact](https://postboxservices.com/contact): contact@postboxservices.com, phone +91 6361139611.
- [Blog](https://postboxservices.com/blogs): articles on deliverability, authentication and email infrastructure.

## Optional

- [Free APRF record generator](https://mx.postboxservices.com/aprf-generator/): builds the _aprf._domainkey TXT record for Aggregate Performance Reporting (the IETF working-group draft draft-ietf-mailmaint-aprf), plus the destination consent record. No login.
- [Free APRF record checker](https://mx.postboxservices.com/aprf-checker/): looks up and validates a published _aprf._domainkey TXT record - the v=APRFv1 version tag, the rua reporting address, and the destination consent record. No login.
- [Hire us on Upwork](https://postboxservices.com/hire-email-deliverability-consultant-upwork).
- [Free email domain health check and DNS tools llms.txt](https://mx.postboxservices.com/llms.txt).
- [Free blacklist check llms.txt](https://bl.postboxservices.com/llms.txt).
- [Free DMARC monitor llms.txt](https://dmarc.postboxservices.com/llms.txt).
- [Free Mail Tester llms.txt](https://mailtester.postboxservices.com/llms.txt).
- [Free TLS-RPT monitor llms.txt](https://tlsrpt.postboxservices.com/llms.txt).
- [Free spoofing and BEC exposure check llms.txt](https://security.postboxservices.com/llms.txt).
- [Free APRF inbox-placement monitor llms.txt](https://aprf.postboxservices.com/llms.txt).
- [Free URL redirect checker llms.txt](https://redirect.postboxservices.com/llms.txt).
- [Free AI discoverability checker llms.txt](https://ai.postboxservices.com/llms.txt).