STARTTLS 503 Bad sequence of commands. Problem with PHPMailer and MailEnable, SMTP and different domains

[MichaelLodes]

Hi,

I am really really helpless now. I am a newbee on this but now spended several days on my problem:

I have a Windows Server 2016 with Plesk Onyx 17.5.3. I want to send mails via PHPMailer 6.0.5.

As Mailserver I use MailEnable. As SSL/TLS Certificate I use Let's Encrypt.

I can send emails to another domain via MailEnable Web Mail interface, but I can't send Emails via PHPMailer. I already reinstalled MailEnable on my server. I reconfigured bruteforcingly all values in SMTP properties in MailEnable Admin Tool.

Everytime I execute PHPMailer script, I get the same error: 503 Bad sequence of commands.

My full error log from PHPMailer is uploaded. SMTP activity log is also uploaded and some more logs, php script and a screenshot of SMTP :
https://kommsafe.de/#/public/shares-dow ... QEFDhd0JgJ


Additional information: My server has different domains: One default domain "h7***.stratoserver.net" and one newly added domain "spatialcontrol.de". Perhaps there is somewhere a misconfiguration because of the several domains? Did I put in the right values in the SMTP properties in the MailEnable Admin Tool?

Please help me. (My skype adress is lomi89@outlook.de)


Best Regards,
Michael

[MailEnable-Ian]

Hi,

The problem here is that your PHP Mailer is trying to send over TLS and issuing a STARTTLS command to the MailEnable SMTP service. However the MailEnable SMTP service is not advertising the STARTTLS extension which indicates you have not enabled it within the SMTP properties.

Navigate within the MailEnable administration console to: servers > localhost > Services and Connectors > SMTP. Right click on SMTP and select properties. Under the "Inbound" tab tick the option for "Allow clinets to establish a secure sessions via STARTTLS". Click OK and then apply and restart the SMTP service. Try your tests again from the PHPMailer.

Telnet test SMTP extensions list to your server:

250-home [0.0.0.0], this server offers 4 extensions
250-AUTH LOGIN
250-SIZE 40960000
250-HELP
250 AUTH=LOGIN

Notice the STARTTLS extension is not advertised. It should look similar to:

250-AUTH PLAIN LOGIN
250-SIZE 20480000
250-HELP
250-AUTH=LOGIN
250-STARTTLS