My out of office

Hi Steph,

Interesting question. Easy to give it a test. I have never seen this arrive, though, but maybe it is just because I have never been in this precise situation.

Many out of office system enables you to only send OOO messages to contacts that are already in your address book.

-Greg

Endless auto-reply loops are almost nonexistent (that isn't what you asked, but you should know) but a mini-loop of 2 replies like you describe isn't impossible. 

The Autoresponder RFC mentions several tactics mailservers should follow for avoiding loops, but it doesn't dictate a complete solution.  Usually, thanks to a combination of legacy headers, proprietary techniques, and compliance with the RFC, loops are prevented.  But not always.  Like Josh said, sending from a mailbox that cannot have an autoresponder takes care of the difference.

If you really want to deploy best-practice email marketing, send from a central, real mailbox that's monitored.  Many case studies of what not to do when sending an email includes sending from an email address that doesn't get monitored - or worse, is indicative of that, e.g., "no-reply@domain.com".  Essentially, what this says is I've sent my message to you, but have no interest in further engaging with you. 

Also, since the "FROM" and "REPLY-TO" addresses are inconsistent in how they work, you should use the same address in both fields within Marketo.