Connect Postmark
Fast and reliable. For marketing, use the Broadcast host — see Step 2.
Postmark is known for speed and reliability. It's transactional-first, but it fully supports marketing email through a separate Broadcast stream — which is what you want for Mailbo.
SMTP settings at a glance
| Setting | Value |
|---|---|
| Server | smtp-broadcasts.postmarkapp.com (use the broadcast host for marketing) |
| Ports | 587 (STARTTLS, recommended) · 2525 · 25 |
| Username | Your Server API Token |
| Password | Your Server API Token (the same token in both fields) |
⚠️ For newsletters/campaigns, use
smtp-broadcasts.postmarkapp.com— notsmtp.postmarkapp.com(that one is for transactional email only). Postmark keeps the two on separate infrastructure to protect deliverability.
Step 1 — Verify your domain
- In Postmark: Sender Signatures → Add Domain → enter your domain → DNS Settings.
- Add the DKIM (TXT) record and the Return-Path (CNAME) record Postmark shows.
- Wait for them to verify (minutes to 24 hours).
Step 2 — Get your Server API Token
- Servers → select your server → API Tokens tab.
- Copy the Server API Token. This single token is used as both the SMTP username and password.
Step 3 — Paste into Mailbo
- Settings → SMTP & sending → click the Postmark tile.
- Sender: From email (on your verified domain) + From name.
- Credentials: Username = Server API Token · Password = the same Server API Token. Make sure the server/host is the broadcast endpoint.
- Save, then Send test email.
Troubleshooting
| Problem | Fix |
|---|---|
| Marketing send blocked | You're on the transactional host — use smtp-broadcasts.postmarkapp.com. |
| Auth fails | Both username and password must be the same Server API Token. |
| Low sending limit | New accounts start limited — request higher limits in Postmark. |
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Last updated 6/15/2026← More in Sending & Deliverability