How do I configure ISPConfig3 mail services for Thunderbird?

Dear ISPConfig3 Experts,
I has been running ISPConfig3 web mail for a long time without any issue.
Lately, I have planned to take advantage of Thunderbird's Mailhops plugin so that I know where a new mail comes from.

However, when I enter mail.mydomain.com into Thunderbird new mail account set up, it can never pass and set up successfully.

Please show me steps to set up IDPConfig3 mail services and DNS records so that I can retrieve email from Thunderbird.

My system is Ubuntu 20.04, nginx, ISPConfig 3.12.

 

Yes, it works!
The main point is - filling the whole ISPConfig3 server as the mail server name; and whole email address as the user name!
Thank you!
Now, I can see everyone`s origin except that he uses dog mail like gmail.

 

Hi Till,
Which one should I choose for IMAP protocol, STARTTLS or SSLTLS?