''LisaatKGComm [[#question-1091962|said]]'' <blockquote> I have been sending an email to a customer for a couple of months, with no response from them. After checking with someone else, we find their email address is incorrect. We never received anything stating the email address is bad, or unable to send. Is there a setting for this? If not, how do we know if an email address has been typed incorrectly? </blockquote> Delivery failure notifications are sent by some servers, but there is nothing in the RFC's requiring them to be sent. Their existence is endangered by spammers. To quote [https://en.wikipedia.org/wiki/Bounce_message Wikipedia ]"''Today, however, it can be common to receive mostly spam emails, which usually utilizes forged Return-Paths. It is then often impossible for the MTA to inform the originator, and sending a bounce to the forged Return-Path would hit an innocent third party. In addition, there are specific reasons why it is preferable to silently drop a message rather than reject it (let alone bounce it):" '' Further reference at Wikipedia is in the form of the article on [https://en.wikipedia.org/wiki/Backscatter_%28email%29 backscatter]. This is in itself considered by many to be SPAM, and sending them has seen mail servers blacklisted as sources of SPAM. So like the good old fashioned postal service, there is no guarantee of delivery, and no guarantee anyone will tell you if your mail is misdirected. The days of a "left address" stamps on an envelope are about over. with paper and electronically. <blockquote> Also, is there an "out of office" automatic reply? </blockquote> See https://support.mozilla.org/en-US/kb/vacation-response