550 must be authenticated

[jpjonesmi]

Mailer has been working fine but recently upgraded. Now I get this message when attempting to send emails. 550 must be authenticated. I didn't change any settings. What went wrong?

 

[stanbusk]

This error is not a MaxBulk Mailer error, it is a server error. The server says you are trying the send emails without authenticating first. Are you sure the ESMTP authentication is activated?

 

[jpjonesmi]

Stan, In the past I had always used POP. I switched it to ESMTP and it worked. Thanks!