SMTP Relay Setup: SMTP Relay Setup: Configure Your Sending Infrastructure for Maximum Deliverability
A technical guide to setting up SMTP relay — authentication, bounce handling, and monitoring.
What is SMTP relay and when to use it
SMTP relay routes outbound emails through a server with established IP reputation. Instead of sending directly from your own server (which may have poor or no reputation), your emails travel through a trusted intermediary that inbox providers already recognize.
Use SMTP relay when sending more than 500 emails per day, when your server IP has poor reputation, or when you need reliable delivery for transactional emails like OTPs and receipts. Direct sending works for small volumes, but scaling without relay guarantees spam folder placement.
SpaceCRM SMTP: Host smtp.spacecrm.net, Port 587 (TLS) or 465 (SSL), Username: your API key. The relay handles IP warmup, reputation monitoring, and bounce processing automatically — you focus on writing emails, not managing infrastructure.
Domain authentication setup
Update your domain SPF record to include SpaceCRM's sending servers. SPF tells inbox providers which servers are authorized to send email on behalf of your domain. Without it, your emails get flagged as unauthorized.
Enable DKIM signing in SpaceCRM domain settings. DKIM adds a digital signature to every email, proving it wasn't tampered with in transit. Both SPF and DKIM are required for full authentication — skip either one and your deliverability suffers.
Set DMARC policy to 'p=none' initially to monitor failures without blocking legitimate email. Once you've confirmed authentication is working, move to 'p=quarantine' or 'p=reject' for maximum protection. Most email clients and frameworks support these settings with no modifications.
Bounce and complaint management
Connect a webhook to receive delivery events: delivered, bounced, complained, unsubscribed. Process hard bounces immediately — do not retry. Hard bounces indicate invalid addresses, and retrying damages your sender reputation.
Soft bounces (temporary failures) should be retried 2-3 times over 24 hours before suppressing. Common causes include full mailboxes and temporary server issues. SpaceCRM handles retry logic automatically.
A complaint rate above 0.1% is a warning signal. Above 0.3% triggers sending limits from inbox providers. Review your complaint rate weekly in SpaceCRM's deliverability dashboard and investigate any campaigns that exceed thresholds.
Monitoring and optimizing delivery
Track delivery rate (target: 98%+), bounce rate (target: under 2%), and complaint rate (target: under 0.1%). These three metrics tell you whether your infrastructure is healthy. If any metric deteriorates, investigate immediately.
Monitor sending volume patterns. Sudden spikes in volume trigger spam filters even with perfect authentication. Increase volume gradually — 20% per week maximum — and monitor inbox placement at each stage.
Use SpaceCRM's inbox placement testing to verify where your emails land across Gmail, Outlook, and Yahoo before launching campaigns. Test every new domain and IP pool before sending to real prospects.