# WHATPORT(2525)

## NAME

port 2525 — SMTP submission (unofficial alternate) — The unofficial fallback SMTP submission port used when ISPs block 25, 465 and 587.

Protocol: TCP  
IANA: ms-v-worlds

## DESCRIPTION

IANA registers 2525 as ms-v-worlds ("MS V-Worlds"), an individual's assignment that nothing uses — the "ms-" prefix is part of the service name, not an attribution to Microsoft. What actually listens here is mail submission: email service providers such as SendGrid, Mailgun and Mailjet offer 2525 as a mirror of their port 587 submission endpoint, with the same STARTTLS and SMTP AUTH requirements, because consumer ISPs and cloud providers frequently block the standard ports outbound. It is a convention, not a standard — the IETF's message submission spec (RFC 6409) defines 587, and no RFC blesses 2525.

## EXPOSURE

**Expose with care.** Acceptable only as a real submission service that requires STARTTLS and authentication, exactly like 587. Because nothing standardises 2525, verify the server actually enforces both rather than assuming it mirrors 587's policy — and never run an open relay here.

## CHECK

```sh
openssl s_client -starttls smtp -connect TARGET:2525
```

## SEE ALSO

- spec — [RFC 6409 — Message Submission for Mail (defines port 587)](https://www.rfc-editor.org/rfc/rfc6409.html) (rfc-editor.org)
- iana — [IANA Service Name and Transport Protocol Port Number Registry — 2525 (ms-v-worlds)](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml?search=2525) (iana.org)

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HTML: <https://whatport.net/2525/> · JSON: <https://whatport.net/2525.json> · full dataset: <https://whatport.net/ports.json>