Filter Rules not applying to sent e-mails

I have a number of custom e-mail addresses aliased to my Mailbox.org account, and I use Filter Rules to tag each e-mail with the e-mail address it's tied to (for, for example, filtering purposes). However, I've noticed an issue: Sent e-mails aren't processed by Filter Rules! For example, given the following Filter Rule…

…if I send an e-mail from example@mydomain.me, it isn't tagged accordingly with that IMAP keyword. It may be undesirable for some users to have their filters apply to sent e-mails – especially filters that, for example, move e-mails to another folder – could perhaps a checkbox along the lines of “Apply to sent e-mails” be implemented?