Port 993 supports IMAPS and Internet Message Access Protocol (UDP reference coverage) across distinct transports. Review each protocol before writing firewall or monitoring policy.
IMAP mailbox access protected by implicit TLS.
Mail clients securely synchronizing folders and messages.
Client to server
Validate certificates, require strong authentication and protect accounts with rate limiting and MFA where supported.
Internet Message Access Protocol (UDP reference coverage) is documented as a network service convention for port 993 over UDP.
Use this reference entry when identifying or validating systems documented to use 993/UDP.
Varies
Confirm the listening process and current vendor documentation before permitting traffic; a listed convention does not prove the active service or its security posture.