Thanks for all your help. The "Accept mail for invalid local addresses" is unchecked and after testing a second time does seem to be working. Not sure why my first test didn't get the failure notification but the second test did get the expected "Delivery failure notification" message.

I am using Mercury32 and am having trouble figuring out how to auto reply to emails that come in to an email address that is not valid. This is normally do to an old email that has been removed or the sender misspelled the address. Either way I would like the sender to know the email was not delivered. I am new to dealing with the email server and if the auto reply in this situation is not recommended please let me know.

Thanks, Ron

I think these messages warrant a personal response.  I speak from a small business perspective when I say this though I think I would do the same for personal mail.  As a business, the personal response allows me to advise a sender of a typo and assure them that their messages has been forwarded.  In the case of a removed address I can take the opportunity to advise them that there messages has been forwarded to their new contact and include new contact details.

Thanks Brain - I our situation I may not be able to reply for hours or even until the next day and there are times someone is waiting for a file to get keep production on time. In this case a more immediate auto response to the sender that the message has not gotten to proper place could get a much faster fix. Also some people are much slower to change the address on their end if they know someone else is forwarding the message on where an auto reply lets them know they need to fix the address if they want the message to go through.

Ron

Hopefully someone else will respond.  My knowledge of Mercury is limited.  I use it to POP mail off of hosted mailboxes so the mail server of my domain host is doing the work that you are trying to do.  We know that mail servers can return undeliverable message notices so I assume Mercury can as well.  Sorry that I can't help with how to make that happen.

There are basically two ways of handling messages for misspelled or otherwise non-existent local users. The most common is probably to set MercuryS to reject them (Configuration / MercuryS SMTP server / General / "Accept mail for invalid local addresses" not checked). The message should then automatically be returned to the sender with a line explaining why it can't be delivered. If MercuryS is set to accept mail for invalid addresses a message to a non-existent local user will cause an error notification to automatically be sent to the sender. If the core option "Send copies of all errors to the postmaster" is checked, the postmaster will get a copy too.

The main disadvantage of the second approach is that it is likely to re-distribute spam as well, as spam messages most often have a forged sender address. This is called backscatter and is not really appreciated by mail server admins.