Is it possible to prevent access through third-party email clients

[Marshal]

SYSTEM INFORMATION
OS type and version	Ubuntu 20.04
Virtualmin version	2.105

I had set up a two factor authentication for Roundcube user, which works fine, despite this it still bypass the 2 factor auths while using a third-party email clients. I want to restrict Roundcube webmail access to only the web interface and prevent access through third-party email clients. any clear instructions or tips would be very helpful. thanks

[Joe]

You could make Roundcube connect to localhost (if it doesn’t already), and configure Dovecot to only listen on localhost. No other mail clients would be able to connect (well, Usermin could, but you could disable that, too).

[Marshal]

Thanks Joe. I did configured Dovecot to only listen on localhost using: (protocols = imap://localhost), with this sadly, [Dovecot IMAP / POP3 Server] refused to start.
Additionally, I tried (protocols = imap) but was I still able to login webmail via mail client.

I would appreciate any assistance at your continence. thanks for your time.

[Joe]

Where did you get this syntax (it’s wrong):

protocols = imap://localhost

You just need to change the listen address, you don’t need to do anything weird.