[Users] How to hide sender IP address and host name?

[Removed GDPR]

Thanks Slavko.

I guess this makes sending through web interfaces which don't expose
the original IP address more secure in the sense: the correspondent who
is not aware of the IP address of the sender could not initiate some
attack of the sending host.

I also suppose that what you shared means that Yahoo's SMTP which does
not reveal the sender's IP address is not up to standard.