I have also raised a forum thread here: https://www.virtualmin.com/node/38366#comment-156235
I found a very strange issue with Email Filters, when it received email sent to it from anyone sending from admin@ or postmaster@
If an email filter is created to forward ALL mail to another address, if you send it from firstname.lastname@example.org (and by anything I mean anything in here, gobbledegook.co.uk), then it goes into the inbox and is not filtered, but if its not admin@anything (even admin1@) , it forwards OK. This also occurs for postmaster, but not hostmaster etc.
This is very strange and people are potentially not getting any emails when sent rom admin@.
Is this is a bug? Or a setting I can fix on the server?
I tried it on two separate mail servers, so for two different domains, and same issue.
Aliases forward OK, so its only email account filters.
This also happens when sending from administrator@ and anything-admin@ and anything-administrator@