[feat] header regex-based spam filter

## Describe the feature

I'd love to see support for evaluating regex not only on the destination address, but on the "From" as well, or even any header, like "Subject".
I like using de-activated regex aliases to discard my catch-all mailbox spam. This is applied on disposable email addresses that I don't use anymore.
But there are some sender domains that are permanent known offenders, like (".[sz]a.com") that I'd like to catch as well. They seem to evade all spam filters and target my main active mailboxes.

## Checklist

- [x] I have searched through GitHub issues for similar issues.
- [x] I have completely read through the README and documentation.