# WHATPORT(993)

## NAME

port 993 — IMAPS (IMAP over implicit TLS) — IMAP mailbox access over TLS, TCP 993.

Protocol: TCP  
IANA registry

## DESCRIPTION

IMAP servers — Dovecot, Cyrus, Courier, and every hosted mail provider — listen on TCP 993, where the TLS handshake begins immediately on connect. RFC 9051 states an IMAP4rev2 server listens on 143 (cleartext) or 993 (implicit TLS), and RFC 8314 recommends 993 as the preferred access port. Mail clients keep long-lived connections here to sync folders and receive IDLE push notifications. It shows on a scan for any host serving user mailboxes.

## EXPOSURE

**Expose with care.** Normal to expose for remote mail clients because TLS is mandatory, but it accepts credentials on every login, so pair it with strong auth and brute-force limits.

## CHECK

```sh
openssl s_client -connect MAIL_HOST:993 -quiet
```

## SEE ALSO

- spec — [RFC 9051 — IMAP Version 4rev2](https://datatracker.ietf.org/doc/html/rfc9051) (datatracker.ietf.org)
- spec — [RFC 8314 — TLS for Email Submission and Access](https://datatracker.ietf.org/doc/html/rfc8314) (datatracker.ietf.org)
- source — [Dovecot (GitHub)](https://github.com/dovecot/core) (github.com)
- iana — [IANA Service Name and Transport Protocol Port Number Registry](https://www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.xhtml) (iana.org)

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HTML: <https://whatport.net/993/> · JSON: <https://whatport.net/993.json> · full dataset: <https://whatport.net/ports.json>