What is an email relay service, and should you use one?
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If you've ever wondered why you can send email from Gmail but it arrives looking like it came from your own domain, an email relay is involved. A relay service accepts your outgoing messages and delivers them through its own infrastructure, handling the SMTP connection, IP management, and deliverability plumbing on your behalf.
Common examples: SendGrid, Mailgun, Amazon SES, and Postmark are all email relay services. So is Google Workspace when you connect a third-party app to send via SMTP. They sit between your application (or CRM, or sequencer) and the receiving mailbox.
Should you use one for cold outreach? For most cold email setups, yes. Running your own mail server is complex, expensive to maintain, and starts with no sending reputation. A reputable relay gives you:
- Established IP pool reputation to borrow from while you warm your domain
- Bounce and complaint handling built in (critical for CAN-SPAM compliance)
- Deliverability monitoring, logs, and webhook events for tracking issues
The tradeoff: You're sharing IP infrastructure with other senders. A well-run relay provider manages this carefully, but if the shared pool gets complaints from other customers, it can affect your delivery too. The better relays segregate cold email senders from transactional senders for this reason.
One thing to get right: Even with a relay, your domain's authentication (SPF, DKIM, DMARC) needs to be configured for that relay. The relay sends on your behalf, so receiving servers check your domain's records. Get those in place before sending any volume. Our free SPF checker confirms the record is live and includes your relay correctly.
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