Hello Jenkins team,

I am using Jenkins 2.176.2 with the Mailer plugin and Office 365 (requires -Dmail.smtp.starttls.enable=true to enable StartTLS).

Emails stopped working after I upgraded the Mailer plugin to version 1.24. I enabled email debugging with -Dmail.debug=true and tested versions 1.20 to 1.24. I found versions 1.20 to 1.23 work fine and email is sent correctly, which I tested with the "Test configuration by sending test e-mail" functionality. When I use Mailer 1.24, useAuth is always false, which gives me this error in the logs and emails are not sent: "530 5.7.57 SMTP; Client was not authenticated to send anonymous mail during MAIL FROM".

Steps to reproduce:

1- Install Mailer 1.24 plugin and configure with Office 365 account and -Dmail.smtp.starttls.enable=true as seen in the picture mailer-config.png (standard Office 365 SMTP client submission configuration)

2- Test email sending by using the "Test configuration by sending test e-mail"

3- Jenkins says "Failed to send out e-mail" with a long java java.net.SocketException and javax.mail.MessagingException included in file jenkins.out-mailer-1.24.log

If any information is missing, please let me know. Thank you!

Ciro