remote mail server authentication fail (cannot find login or plain auth method)

I'm trying to configure mail server settings for notifications but I get the following errors :

"Authentication method mismatch. Please confirm the authentication method support for LOGIN or PLAIN on the mail server"

I check my mail server (MailEnable v9) and it DOES have LOGIN command :

220 ******** ESMTP MailEnable Service, Version: 9.03-- ready at 08/17/16 11:32:31
ehlo sophos.com
250-***** [*******], this server offers 5 extensions
250-AUTH LOGIN
250-SIZE 30720000
250-HELP
250-AUTH=LOGIN
250 STARTTLS
QUIT
221 Service closing transmission channel

I have multiple customer sending to this mail server via authentication and never had this issue ...

I guess it could be an issue with the following line wich is send by mailenable and other mta to help legacy smtp client that have broken compatibility with new ESMTP RFC : "250-AUTH=LOGIN"