support for mail.de user names

[pq2]

Steps To Reproduce

1. Create a mail.de account and set a username for this account.
2. Run the email setup script from the main menu.
3. While running the script, select mail.de as your email provider.
4. Complete the script with the account details from step 1.

Expected Result

Sending emails is set up correctly.

Actual Result

Mail sending does not work.
The email provider mail.de now supports the creation of a user name that differs from the local part of the email address. If you create one, authentication on the SMTP server is performed using the user name and no longer using the email address. However, this is not yet supported by the mail script in addons/smtp_mail.sh. In /etc/msmtprc the field user must be set to the chosen user name.

Screenshots, Videos, or Pastebins

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Additional Context

No response

Build Version

irrelevant

Environment

By using the scripts

Environment Details

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