What is an SMTP relay? A Clear Guide

An SMTP relay is a service that accepts your mail and delivers it on your behalf, handling authentication, reputation and retries. It is how apps and servers send email reliably at scale.

Why it matters

Getting an SMTP relay right keeps you compliant and lands more mail in the inbox. See the deliverability checklist.

How Rainmail helps

Rainmail sends from your own domain on a dedicated, isolated IP with SPF, DKIM, DMARC, reverse-DNS and managed warm-up handled for you, plus an AI watching list health and deliverability — and it welcomes senders SES, SendGrid and Mailchimp reject, from $8. Run the free checker or see plans.