Problem to configure an Inbox server

Hello from France

I can’t get the Inbox server of a WP Mailster v1.8.1 (on a WordPress v6.0.1) hosted by the French service provider OVH to work. I tried the settings indicated in the WP Mailster doc ( https://wpmailster.com/doc/mail-provider-settings/ ) or those of OVH without success.
According to the documentation, for OVH, you must use the POP3 protocol on port 110 without secure authentication or using SSL/TLS encryption.
A connection test returns the following error in the logs:
SECURITY PROBLEM: insecure server advertised AUTH=PLAIN
Retrying PLAIN authentication after [AUTH] Authentication failed.

Do any of you have any idea where the problem could come from?
and how to fix it?

Thank you in advance for your answers ?? .

Best regards.