IMAPS
What is Port 993?
Port 993 is the standard port for IMAP over SSL/TLS (IMAPS), providing encrypted email retrieval and management. When an email client connects to port 993, a TLS handshake occurs immediately before any IMAP commands are sent, ensuring all communication — including authentication credentials and email content — is encrypted. This is the recommended way to access email via IMAP and is supported by all major email providers including Gmail, Microsoft 365, Yahoo Mail, and others. IMAPS provides the same functionality as IMAP on port 143 — folder management, server-side search, message flags, and multi-device synchronization — but with the critical addition of transport security. RFC 8314 recommends using implicit TLS on port 993 as the preferred method for securing IMAP connections.
Common Uses
- Secure multi-device email access
- Enterprise email client configuration
- Mobile email applications with TLS
- Automated email processing with encryption
Technical Details
Copy-paste commands to check port 993 (IMAPS) from your terminal
Test connectivity
nc -zv example.com 993
curl -v --max-time 5 http://example.com:993/
telnet example.com 993
nmap -p 993 -sV example.com
(echo > /dev/tcp/example.com/993) 2>/dev/null && echo "open" || echo "closed"
Open port in firewall
sudo ufw allow 993/tcp
sudo iptables -A INPUT -p tcp --dport 993 -j ACCEPT
sudo firewall-cmd --permanent --add-port=993/tcp && sudo firewall-cmd --reload
Security Considerations
IMAPS provides transport encryption, but accounts are still vulnerable to credential attacks. Implement multi-factor authentication, monitor for login anomalies, and use app-specific passwords. Ensure the server's TLS certificate is valid and from a trusted CA. Disable support for TLS 1.0/1.1 and weak cipher suites.
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