If you’re using POP3 as opposed to IMAP then sometimes you will receive an error when trying to send mail from outlook. “None of the authentication methods supported by this client are supported by your server“. This is because for added security the server will deny connections from an insecure source.
First double check you have the setting “Log onto incoming mail server before sending mail” on the “outgoing” tab checked in your email client like Outlook. You can find this by clicking “file” and “account settings” double-click the account with the email sending issue. Then, if you still can’t send mail, follow the below.
- Login to WHM with the root account
- Navigate to Exim Configuration Manager > Security > Require clients to connect with SSL or issue the STARTTLS command before they are allowed to authenticate with the server.” from “On” to “Off
Exim will restart then you should try to send your email again.