I am a little confused as to why I can't set-up autoforwarding from my own mail server.

I use Dynu to act a a mail relay.

So, if I send a message from bob@bob.com to nathan@mydommain.com but I have an autoforward set to nathan@gmail.com, dynu gives me an error of "554 Invalid From Address. (in reply to end of DATA command". I am guessing this is because bob@bob.com is not considered by dynu as a valid user - even though it's a forward from an account which can send email.

Is there any way around this? Spent several hours on google but failed to find anything that actually helps.

thanks
Mark

I think your assumption is correct. When you look at forwarded email in mydomain.com mailbox, the sender is from bob@bob.com. So I assume that Dynu does not treat it as a registered domain.

However, if you send a email from mydomain.com, the sender will be nathan@mydomain.com. So Dynu will let it go through.