Server's that check SPF, and domains that are setup to deny un-authorized servers cause issues with server side mail forwarding. Clearly this is a problem caused by SPF, and I realize that this is probably a MTA issue rather than Virtualmin. However, I thought I should bring it up here anyway.
Example:
The following forward is setup: user@company.com -> personal@bigmailprovidor.com
The domain "morante.net" has the following SPF record: v=spf1 mx mx:venus.morante.net ip4:205.232.175.67 -all
bigmailprovidor.com does SPF checking.
I send a message to user@company.com, I get:
550 5.7.1 Sender Policy Framework of `morante.net' domain denied your IP address. (in reply to MAIL FROM command)
Microsoft Exchange would normally do server side forwarding by replacing the from address with the mailbox address. Can virtualmin have an option to do the same? I always hated this "feature", but SPF makes it a necessity now.
What would it take to have virtualmin use SRS? http://www.openspf.org/SRS
https://www.virtualmin.com/node/48212