However, it has a really nifty feature that makes this idea work much better, in my opinion. You can configure FastMail to use "virtual domains" that will reroute b@a.example.com to a+b@example.com. (To use this, you need a MX record for *.example.com, but that's fine.)
So, for example, I may sign up for a SpammyService with the email spammy@myemail.mydomain.com. Then all emails from SpammyService will be redirected to myemail+spammy@mydomain.com, which will then be filed in the appropriate folder.
This lets me (1) get around services that disallow plus signs in emails and (2) not let an automated system know that I'm auto-filing their emails (and potentially deleting them, etc.)
However, it has a really nifty feature that makes this idea work much better, in my opinion. You can configure FastMail to use "virtual domains" that will reroute b@a.example.com to a+b@example.com. (To use this, you need a MX record for *.example.com, but that's fine.)
So, for example, I may sign up for a SpammyService with the email spammy@myemail.mydomain.com. Then all emails from SpammyService will be redirected to myemail+spammy@mydomain.com, which will then be filed in the appropriate folder.
This lets me (1) get around services that disallow plus signs in emails and (2) not let an automated system know that I'm auto-filing their emails (and potentially deleting them, etc.)