I use my MUA's
KMail built-in filter facility. I also tried
sieve scripts, but did not succeed, although my e-mail provider supports them. Maybe I have to edit them through the web interface, but I rarely use that because a local e-mail frontend like
Kontact/KMail is more convenient. Browse through
/usr/ports/mail, there are plenty of tools to sort your incoming mail into folders when the mail arrives or gets fetched via POP or IMAP. For shure a so-called
free e-mail provider (where you pay with your data instead of money) will not allow you to automagically sort their advertising mailings into the trash folder...
See here for
two alternative e-mail+ (cloud storage) providers at the cost of 1€/month. At least
Posteo supports sieve scripts, very likely
Mailbox.org, too. Many lists offer a
digest mode, i.e. you get many mails bundled, once or twice a day, instead of all the posts separate.