smtplib.py does not follow RFC2821 requirements

[GentleRV]

Bug report

Bug description:

RFC 2821 require and must give FQDN in set up and EHLO handling.
For now this RFC 2821 is not implemented to reach those requirements.
The current behavior triggers security problems and false connections to servers to try to hack, deliver viruses and spam
Protection from mailserver's becomes problematic using the current smtplib.py in programs like erpnext as they rely fully in this library

CPython versions tested on:

3.14

Operating systems tested on:

Linux

[picnixz]

The docs of smtplib say:

If specified, local_hostname is used as the FQDN of the local host in the HELO/EHLO command. Otherwise, the local hostname is found using socket.getfqdn().

So we already provide that functionality.