Configure Mail Client for Mailu

This guide shows how to configure desktop and mobile mail clients to connect to the Mailu server at mail.kup6s.com.

Connection Settings

Incoming Mail (IMAP)

  • Server: mail.kup6s.com

  • Port: 993

  • Security: SSL/TLS

  • Authentication: Normal password

  • Username: Full email address (e.g., user@kup6s.com)

Outgoing Mail (SMTP)

  • Server: mail.kup6s.com

  • Port: 465 (SMTPS) or 587 (Submission with STARTTLS)

  • Security:

    • Port 465: SSL/TLS

    • Port 587: STARTTLS

  • Authentication: Normal password

  • Username: Full email address (e.g., user@kup6s.com)

Recommended: Use port 465 (SMTPS) for better compatibility with firewalls.

Quick Configuration Examples

Thunderbird (Desktop)

  1. Add Account:

    • Email: user@kup6s.com

    • Password: Your account password

    • Click “Continue”

  2. Manual Configuration:

    • Incoming: IMAP, mail.kup6s.com, Port 993, SSL/TLS, Normal password

    • Outgoing: SMTP, mail.kup6s.com, Port 465, SSL/TLS, Normal password

    • Username (both): Full email address

  3. Test Settings and click “Done”

Apple Mail (macOS/iOS)

  1. Add Account → Other Mail Account

  2. Enter Details:

    • Name: Your Name

    • Email: user@kup6s.com

    • Password: Your account password

  3. Apple Mail auto-detects settings, verify:

    • IMAP: mail.kup6s.com:993 (SSL)

    • SMTP: mail.kup6s.com:465 (SSL)

Android (Gmail app)

  1. Add Account → Other

  2. Email: user@kup6s.com, click “Manual Setup”

  3. Personal (IMAP):

    • IMAP server: mail.kup6s.com

    • Port: 993

    • Security type: SSL/TLS

  4. SMTP Settings:

    • SMTP server: mail.kup6s.com

    • Port: 465

    • Security type: SSL/TLS

    • Username: Full email address

Outlook (Desktop/Mobile)

  1. Add Account → Advanced setup → IMAP

  2. Incoming Mail:

    • Server: mail.kup6s.com

    • Port: 993

    • Encryption: SSL/TLS

  3. Outgoing Mail:

    • Server: mail.kup6s.com

    • Port: 465

    • Encryption: SSL/TLS

Alternative Ports

Protocol

Port

Security

Notes

IMAP

993

SSL/TLS

Recommended

SMTP

465

SSL/TLS (implicit)

Recommended - works everywhere

SMTP

587

STARTTLS (explicit)

Alternative if 465 blocked

POP3

995

SSL/TLS

Not recommended (use IMAP)

Note: Port 25 (SMTP) is for server-to-server mail only, not for client connections.

Testing Connection

Test IMAP Connection

openssl s_client -connect mail.kup6s.com:993 -quiet

Expected response:

* OK [CAPABILITY IMAP4rev1 ...] Dovecot ready.

Test SMTP Connection

openssl s_client -connect mail.kup6s.com:465 -quiet

Expected response:

220 mail.kup6s.com ESMTP Postfix

Troubleshooting

“Cannot Connect to Server”

  1. Check network: Ensure ports 993, 465, 587 aren’t blocked by firewall

  2. Verify DNS: nslookup mail.kup6s.com should return 167.233.14.203

  3. Test TLS: Use openssl commands above to verify TLS handshake

“Certificate Error” or “Untrusted Certificate”

  • The server uses a valid Let’s Encrypt certificate

  • If you see certificate warnings, check system date/time

  • Older devices may need system updates for Let’s Encrypt root CA

“Authentication Failed”

  1. Verify credentials: Try logging into webmail at https://mail.kup6s.com

  2. Check username: Must be full email address, not just username

  3. Password special characters: Some clients require escaping

“Connection Times Out”

  • Port 465/587/993 may be blocked by network/ISP

  • Try mobile data to rule out network restrictions

  • Contact network administrator if on corporate network

Security Notes

  • All connections use TLS encryption - your password is never sent in plaintext

  • TLS 1.2 minimum enforced for all mail protocols

  • Modern cipher suites only (ECDHE with AES-GCM or ChaCha20-Poly1305)

  • Certificate validated by Let’s Encrypt (trusted by all major OS/browsers)