Internet-Security.com TCP port 993 details

TCP port 993 is used by IMAPS (Internet Message Access Protocol over SSL/TLS), the encrypted IMAP service.
Major email services expose IMAPS on 993, including Gmail (imap.gmail.com), Microsoft 365/Outlook.com (outlook.office365.com or imap-mail.outlook.com), Yahoo Mail (imap.mail.yahoo.com), and Apple iCloud Mail (imap.mail.me.com).
Common IMAP server software that listens on 993 includes Dovecot, Cyrus IMAP, Courier-IMAP, Microsoft Exchange Server, Zimbra Collaboration Suite, Kerio Connect, and hMailServer.
Web hosting platforms like cPanel/WHM typically run Dovecot on port 993 for customer mailboxes.
Email clients such as Microsoft Outlook, Apple Mail, Mozilla Thunderbird, and mobile Mail apps connect to servers on 993 when configured for secure IMAP.
IMAPS endpoints on 993 are frequent targets for credential-stuffing and brute-force login attacks, so operators commonly deploy rate limiting, lockouts, and MFA.

TCP 993