Demo
Watch a rewrite in action.
Walk through exactly what PostMerge does to each email as it passes through the rewriting layer.
Before and after PostMerge
Every header and calendar attachment — rewritten, consistently, in under 200ms.
Original — leaves acquiredco tenant
mailto:alice.johnson@acquiredco.com
ATTENDEE;CN=Client:
mailto:client@external.com
After PostMerge — delivered to internet
mailto:alice.johnson@newbrand.com
ATTENDEE;CN=Client:
mailto:client@external.com
Every field rewritten · DKIM re-signed with your unified domain's key · Delivered in <200ms
The process
How PostMerge works
Configure outbound connector
Point your M365 or Google Workspace outbound connector to your PostMerge relay endpoint. Each tenant gets a unique address like yourorg.relay.postmerge.io.
Upload your mappings
Upload a CSV mapping source domains to the unified domain, or sync from your directory. Set blanket rules and per-sender overrides.
Verify DNS records
Add SPF, DKIM, and DMARC records for your unified domain. The portal's built-in DNS checker verifies everything is correct before you go live.
Go live
Enable rewriting. Every outbound email is intercepted, rewritten, re-signed with DKIM, and delivered with your unified domain. Monitor everything on the dashboard.
Want to try it yourself?
Start a free trial and rewrite your first email in minutes. No credit card required.
Request Early Access