Server does not support TSL Connections

Email & Webmail | Updated March 2026

The "Server does not support TLS connections" error in email clients means the encryption settings do not match what the server expects. Our servers fully support TLS, but the port and encryption type must be paired correctly. Mismatching them (like using STARTTLS on a port that expects full SSL) triggers this error.

In This Guide

Correct Port and Encryption Settings
Common Mistakes
Client-Specific Settings
Testing Your Connection

Correct Settings

Use these port and encryption combinations

IMAP: Port 993 with SSL/TLS, or Port 143 with STARTTLS
POP3: Port 995 with SSL/TLS, or Port 110 with STARTTLS
SMTP: Port 465 with SSL/TLS, or Port 587 with STARTTLS

Do not mix them. Port 993 requires SSL/TLS, not STARTTLS. Port 143 requires STARTTLS, not SSL/TLS.

01. Correct Port and Encryption Settings

There are two encryption methods and they are not interchangeable:

SSL/TLS (implicit encryption) - The connection starts encrypted immediately. Used with ports 993 (IMAP), 995 (POP3), and 465 (SMTP). This is the recommended setting for most email clients.

STARTTLS (explicit encryption) - The connection starts unencrypted, then upgrades to TLS via the STARTTLS command. Used with ports 143 (IMAP), 110 (POP3), and 587 (SMTP).

Both are secure once the encryption is established. The difference is when the encryption starts. The error occurs when you tell your email client to use STARTTLS on a port expecting immediate SSL (or vice versa).

02. Common Mistakes

Port 993 with STARTTLS - This is the most common misconfiguration. Port 993 expects immediate SSL/TLS, not STARTTLS. Change the encryption type to SSL/TLS.

Port 587 with SSL/TLS - Port 587 expects STARTTLS. Either switch to STARTTLS, or change the port to 465 and keep SSL/TLS.

"None" or "No encryption" - Our servers require encryption for all email connections. Ports 25, 110, and 143 without any encryption will be rejected.

Wrong server hostname - The incoming and outgoing server should be mail.yourdomain.com. Using the bare domain or an IP address may cause certificate mismatch errors on top of the TLS error.

03. Client-Specific Settings

Outlook: Go to File > Account Settings > double-click your account > More Settings > Advanced tab. Set IMAP to 993 SSL/TLS and SMTP to 465 SSL/TLS. See our Outlook setup guide.

Thunderbird: Go to Account Settings > Server Settings. Set the port and "Connection security" dropdown. Thunderbird uses "SSL/TLS" and "STARTTLS" in the dropdown. See our Thunderbird guide.

iPhone/iPad: Go to Settings > Mail > Accounts > your account > tap the account name > SMTP/Incoming settings. Set the ports and toggle "Use SSL" on. See our iPhone email guide.

Android: Settings vary by manufacturer. Look for "Security type" in the incoming/outgoing server settings. See our Android email guide.

04. Testing Your Connection

If you've set the correct ports and encryption and still get the error:

Test webmail first - Log in at https://yourdomain.com/webmail. If webmail works, the email account and password are correct and the problem is in your client's configuration.

Check for firewall blocks - If you've entered the wrong password multiple times, your IP may have been blocked. Use our firewall unblock tool to check.

Check SSL certificate - If you get both a TLS error and a certificate warning, the mail server's SSL certificate may need renewal. Contact support if you see certificate-related errors.