Last week we sent an outlook email out designed to look like it was coming from someone specific within the organization using the from as his email address but the reply-to as an info address. We did it this way, as we always do, to prevent the event where whom it looks like it is coming from won’t actually be receiving any of the reply emails including OOO/auto reply’s.
With that being said, that was not the case. Our colleague wound up receiving all the auto-reply’s to his email directly and nothing came to the info email address.
We have never had an issue with this in the past and when opening a ticket with Marketo they expressed that regardless of what the "reply-to" address it that by default the auto-reply's will go to the from.
Has this always been the case? - We feel that this doesn't/hasn't happen in the past and wondering if anyone has experienced the same issue.
No, nothing's changed.
RFC 3834, the closest to an autoresponder standard, has long been clear that Reply-To: is only for replies from humans (i.e. in response to real user interaction in a mail client) not replies from machines (timed/triggered responses).
The RFC also frowns upon using the From: address, instead preferring the SMTP-level envelope sender. (But envelope sender is typically the same as the From: address for person-to-person messages, so without controlled testing you don't know what logic the mail server used!)
Not every mail server obeys the RFC, so the Reply-To: will receive a subset of autoresponses. Wouldn't use the expression "by default," though, in the sense that each mail server will reliably send to the same destination. But Reply-To has always been in the minority. See also Different Email Addresses in the From and Reply-To Lines and here.
In sum, whatever you thought was happening before, wasn't actually happening.