Features
Everything you need to unify email after a merger.
PostMerge handles every aspect of email domain rewriting so your combined organization presents a single, professional brand from day one.
Core Engine
Complete header rewriting
MIME Header Rewriting
Rewrites domains in all configurable headers: From, To, CC, BCC, Reply-To, Return-Path, Sender, Message-ID, References, In-Reply-To, and any custom headers you specify.
ICS Calendar Rewriting
Parses text/calendar MIME parts and .ics attachments per RFC 5545. Rewrites ORGANIZER, ATTENDEE, and mailto: URIs so calendar invites show the unified domain.
DKIM Re-signing
After rewriting, messages are re-signed with the unified domain's DKIM private key. Keys are stored in AWS KMS, encrypted at rest, and never leave the signing process. Deliverability preserved across all major providers.
Inbound Reverse Rewrite
When someone replies to alice@newbrand.com, PostMerge reverse-rewrites the headers back to alice@acquiredco.com and delivers to the original tenant. SRS validation ensures reply integrity so nothing gets lost in transit.
Flexibility
A rule engine built for real orgs
Not every sender should be treated identically. PostMerge gives you full control with layered rules.
Blanket Rules
Apply domain rewriting to every sender in the organization with a single rule. Set it once and forget it.
Per-sender Overrides
Executive assistants, shared mailboxes, service accounts, or noreply addresses can all have different rules or be excluded entirely.
Header Selection
Choose exactly which MIME headers to rewrite per rule. Full control, zero surprises. Preview changes before going live.
Self-service Portal
Everything in one place
Mapping Upload
Upload CSV or Excel mapping files to define source → unified domain rules. Async validation with clear, actionable error reporting.
Rewrite Simulator
Paste a raw email and see exactly how PostMerge would rewrite it — before you go live. No surprises.
Message Tracking
Full audit trail for every rewritten message, with before/after header diffs and the rules applied.
Dashboard
Email volume, rewrite success rates, bounce and complaint metrics at a glance. Catch issues before they become problems.
DNS Verification
Built-in DNS checker validates your MX, SPF, DKIM, and DMARC records and flags anything that would hurt deliverability.
Directory Sync
Sync user lists from Microsoft Entra ID or Google Workspace automatically. Always up to date as your org changes.
Security
Enterprise-grade, by default
Encryption at rest
AES-256 via AWS KMS for all stored emails, DKIM keys, and database records.
Encryption in transit
TLS 1.2+ everywhere: SMTP STARTTLS, HTTPS APIs, and database connections.
Tenant isolation
Row-level security, S3 prefix separation, and JWT-enforced tenant context.
Audit trails
Every rewrite logged with before/after headers, rules applied, timestamps, and actor identity.
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