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How to Smtp relays

Published October 4, 2024 · Updated July 19, 2026 · SMTP & Deliverability

SMTP relays are the quiet infrastructure that carries your email from where it is created to where it is read. Understanding how relays work - and choosing a good one - is central to reliable delivery. Here is a clear overview of SMTP relays.

How SMTP relays work

When you send, your message passes through one or more relays that accept and forward it, applying authentication and a sending IP along the way. The reputation of that relaying IP heavily influences whether the message reaches the inbox.

Choosing the right relay

  • Dedicated IP - reputation you control.
  • Real volume without hidden caps.
  • Automatic SPF, DKIM, DMARC.
  • Easy integration on port 587.
The decision that matters: shared relays share reputation; a dedicated relay isolates yours. For email that matters, dedicated wins.
Related reading: Email Domain Management · Email Warmup Guide: How to Build Sender Reputation on a New SMTP Server · test your email deliverability
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Frequently asked questions

What are SMTP relays?

Servers that accept and forward your outgoing email toward recipients, applying authentication and IP reputation that decide inbox placement.

How do I choose an SMTP relay?

Prioritise a dedicated IP, real volume, automatic authentication, and simple port-587 integration.