[Grhm]

You are plagued by spam and ask for advice.
I will pass on the advice I read in this forum some years ago and followed:
Buy your own domain name and use a different address on that domain for each purpose.
I did that and am very glad I did.
Nowadays I get maybe one piece of spam a week.
(Re e-mail clients - personally I have never seen the point of them - I can think of nothing an individual might reasonably want to do with e-mail that can't be done using Fastmail's web interface.)