I created a rule for incoming mail containing certain words in the subject.
Rule is to mark as read and then archive.
Rule only works by manually clicking “Process entire mailbox”.
One caveat that may be the issue but still makes it a bug, is that the emails I’m trying to auto-delete are forwarded to anoter email address than the account I have setup in MailSpring.
Let me explain (english is not my first language)
Specific example. Every day I get Domain Agregate Reports sent to dev@mydomain.com. This specific email address is forwarded to a gmail address me@gmail.com.
Rule says:
If email To = dev@mydomain.com then Mark as read and delete.
This doesn’t happen. But, if I go into the Mail Rules and click “Process Entire Inbox” it clears these emails out.
I’m not sure if the forwarding address is confusing the rule mechanics, but it’s a little annoying. If I have to go into settings to make the rule work, then I might as well not have the rule 
Thank you for a great app…
~j