Setup Guides
Provider-Specific Email Setup Guides
Documentation that starts where the official docs stop: each guide walks the exact setup for one provider, then covers the failures we actually find in audits - the forgotten toggle, the truncated record, the default signature that never aligns. Every guide ends with a way to verify the fix on a real message.
Microsoft 365 DKIMThe selector1/selector2 CNAMEs everyone forgetsWhy the tenant-default onmicrosoft.com signature never aligns, the 5-step Defender walkthrough with exact CNAME shapes, and the six failures that break it.Read the guide →Google Workspace DKIMThe google._domainkey record and the gappssmtp trapGenerate the key, survive your DNS host's TXT limits, remember Start authentication - and the six failures that leave Workspace mail signing as gappssmtp.com.Read the guide →Zoho Mail SPFOne record, the right include and the 10-lookup trapThe v=spf1 include:zohomail.com record, the Admin Console verification, and the five failures that break Zoho SPF - including the include:zoho.com permerror many guides still teach.Read the guide →BIMIYour logo in the inbox, and when you need a VMC or CMCPublish BIMI on top of DMARC enforcement - the SVG Tiny 1.2 P/S logo, the default._bimi record, and the VMC-vs-CMC decision: what shows in Gmail, Yahoo and Apple, and the blue verified check.Read the guide →
More on the wayExchange Online sending limits and the restricted-entities trap, and more provider guides are queued. Meanwhile, test any setup with Postbox Mailtester.
Not sure which part of your setup is broken?