How to Fix “None of the authentication methods supported by this client are supported by your server”

You can receive email, but every message you send fails with this error:

Sending reported error (0x800CCC80): None of the authentication methods
supported by this client are supported by your server.

The mail app and the server could not agree on a safe way to log in to the outgoing (SMTP) server. It is almost always a setting in the mail app, and takes a minute to fix.

Quick answer

In your mail app's outgoing (SMTP) server settings:

1. Turn on My outgoing server (SMTP) requires authentication, using the same username and password as for incoming mail.
2. Set encryption and port to one of these pairs:
   • SSL/TLS on port 465, or
   • STARTTLS (Outlook calls it TLS) on port 587.
3. Save and send a test message.

Microsoft

Why it happens

There are two common causes:

• The app does not log in to the outgoing server at all. Most servers only let you send mail after you log in, so they reject the app. Microsoft
• The app logs in without encryption. Many servers, including every cPanel server by default, only offer a login over an encrypted connection. If the app's encryption is set to None, the server offers it no login method it accepts, which produces exactly this error. cPanel

Fix it in Outlook for Windows (classic)

1. Open File › Account Settings › Account Settings.
2. Select the email account and click Change.
3. Click More Settings and open the Outgoing Server tab.
4. Tick My outgoing server (SMTP) requires authentication and choose Use same settings as my incoming mail server.
5. Open the Advanced tab.
6. Under Outgoing server (SMTP), choose one of these:
   • Port 465 with encryption SSL/TLS, or
   • Port 587 with encryption STARTTLS (older versions show TLS).
7. Click OK, then Next and Finish. Outlook sends a test message to check the settings.

Microsoft's other suggestion, Log on to incoming mail server before sending, also works on some servers, but proper SMTP authentication (step 4) is the better fix. Microsoft

Fix it in other mail apps

The setting names differ, but the idea is the same. In the outgoing / SMTP server settings for the account:

• Authentication: Normal password (Thunderbird), Password (Apple Mail), or the account's username and password.
• Connection security: SSL/TLS with port 465, or STARTTLS with port 587. Never None.

In Apple Mail on a Mac, these are in Mail › Settings › Accounts, under Server Settings › Outgoing Mail Server: untick Automatically manage connection settings to edit the port and choose Use TLS/SSL.

Settings for email on a cPanel server

For a mailbox hosted on cPanel, use these values. Replace example.com with your domain:

The exact settings for each mailbox are in cPanel › Email › Email Accounts › Connect Devices.

If the app warns that the certificate does not match mail.example.com, use the server's own hostname as the server name instead. Your host can tell you what it is.

For server administrators: don't turn off the SSL requirement

On a cPanel server, the error can also be made to disappear by turning off Require clients to connect with SSL or issue the STARTTLS command before they are allowed to authenticate with the server in WHM › Service Configuration › Exim Configuration Manager. cPanel

Leave it on. Turning it off lets mail apps send passwords over the internet unencrypted, where anyone on the same network can read them. Fix the mail app's settings instead.

Still not working?

• Port 465 or 587 times out. Your internet provider or a firewall may block it. Try the other port, or try from another network such as a phone hotspot.
• The password is rejected. Reset the mailbox password in cPanel and enter it again in the app.
• Only one device has the problem. Compare its settings with a device that works, or remove the account from the app and add it again.