993
Encrypted IMAP email access over TLS (IMAPS)
IMAP over SSL/TLS
What is port 993?
IMAPS on port 993 is the TLS-encrypted version of IMAP (port 143). TLS is established immediately upon connection, protecting credentials and email content in transit. It is the recommended option for email access in any mail client. Virtually all modern email providers — including Gmail, Outlook, and Yahoo — support IMAPS.
Quick checks
$
nc -zv example.com 993
$
nmap -p 993 example.com
$
telnet example.com 993