I'm familiar with filtering settings, but how can I filter something that's different each time?
Your post's body asks about filters. "Filters" require some sort of a match, even a partial one. If there is nothing to match, then filtering is not an effective tool.
But your title asks to "get rid of", and that's a broader goal. If you cannot filter based on sender, then you detect spam by the contents. There are a host of tools and approaches to detect and respond to spam emails:
- inspect attachments and links for malicious or blocked content
- inspect the content of the message body for common or malicious content
- inspect the content of the message body for anomalous content
There is a massive industry around and a thousand approaches to the above.
It is trivial for spammers/phishers to send a million emails from a million different, unrelated sources. Trying to block each one is like playing "whack-a-mole".
Looking at what they send is the more effective approach.
The apparent "FROM" is readily faked. Look at the full email headers for several of the spams, odds are good there is a common identifier buried inside that you can use as a filter, it may even be as simple as the originating IP.
Don't forget that your filter need not be an EQUAL match. You may find that a substring match using CONTAINS will work best.
There isn't any clear-cut method, but you could:-
Use your intuition.If the sender's address seems sketchy(either the apparent randomness in the e-mail address or the obscurity in the domain name) or the e-mail is simply from someone who you don't know.
You could allocate an hour or two for a one-time organisation of your mailbox,maybe creating subfolders for different purposes such as one for your newsletters, one for e-mails from your colleagues etc. , so that any e-mail you receive that does not automatically fit into these subgroups can be treated as spam.
(A radical one,but depends on a lot of factors such as your profession and visibility) Create a new e-mail address and jot off a text/e-mail to your associates about the change,then abandon the current one.
(I'm assuming that your e-mail may have been exposed in breaches,making it impossible to avoid spam)