SMTP Routing Configuration Guide
Configure multi-outbox custom rotation loops for cold campaigns
MailCloud distributes outbound email campaign volumes across a pool of custom SMTP and IMAP servers. By implementing multi-outbox rotation, you prevent any individual server from exceeding safe sending thresholds. This guide details setup requirements.
1. Domain and Authentication Setup
Before linking custom SMTP hosts, ensure your domains have the following DNS TXT parameters configured to guarantee inbox delivery:
- SPF (Sender Policy Framework): Add `v=spf1 include:spf.yourhost.com ~all` to declare authorized servers.
- DKIM (DomainKeys Identified Mail): Generate and host your host's public key signature selector.
- DMARC (Domain-based Message Authentication): Enforce a policy to monitor spoofing, e.g., `v=DMARC1; p=quarantine; pct=100`.
2. Mapping Outbox Settings inside Dashboard
Navigate to the **Outboxes** panel inside your Dashboard workspace and specify the following details:
3. Connection Health Verification
Once you hit save, our background worker initiates an instant SMTP connection handshake and checks folder access permissions on IMAP. This ensures we can monitor replies. If tests fail, verify if:
- App-specific passwords are enabled (highly recommended for Google and Microsoft profiles).
- Firewalls or custom mail filters are not blocking connections from MailCloud server IPs.
Campaign Rotation & Cooldown Rules
To keep your reputation high:
- Always enable the **Warmup Loop** setting, which starts sending volume at 10/day and increases by 5 each day.
- Enable randomized send intervals (180 to 300 seconds delay between emails).
- Limit individual domain names to no more than 3 associated outboxes.