Migrate to aiosmtp

[matrixise]

[sebix]

The used smtpd module has been removed in Python 3.12, with https://pypi.org/project/aiosmtpd as its successor

[matrixise]

Hi @sebix,

Not wrong, I had not followed the removal of smtpd in 3.12. Thank you for the information. Now I just need to find the time to move all the code to aiosmtpd.