Have you ever received a bounce message that says “We do not relay” or “Mail loops back to myself”? Wondering what that means? I get this question often enough, that I thought it would be useful to break it down for you here.
Both of these error messages mean that the site you’re trying to send mail to is misconfigured. Neither of these errors typically indicates a problem with you or your ISP.
“We do not relay” (or "Relaying denied") means “It looks like you’re trying to relay mail through me, and I don’t allow that.” In this instance, the destination mail server is incorrectly configured. It doesn’t know that it’s supposed to handle mail to the domain you’re contacting, so it’s thinking that it’s being asked to forward mail on for an unknown party. Most mail servers don’t allow this, because “open relaying” was a popular method of sending spam for many years. This doesn’t mean you’re a spammer. It just means that the remote server is configured incorrectly. They are probably (accidentally) blocking all inbound mail due to this issue.
“Mail loops back to myself” is a similar issue. In this case, the mail server is smart enough to have looked up the MX (mail exchange) records for the remote domain. It notes that it in fact is the destination server for the mail. But, it hasn’t been configured to receive mail for this domain. So, the server is telling you, “I know that mail to this site is supposed to end here, but I’m not configured for that, so I don’t know what to do with this mail.” This is another example of an error message that probably indicates that all mail to that site is being bounced, because their server is not configured correctly.
If the server can tell that DNS records indicate that it’s supposed to accept mail for a given domain, why doesn’t it just automatically accept the mail? A mail server wouldn’t automatically accept mail for domains pointed at it via DNS, because that would be a risk to the server’s security and stability. Bad guys all around the world could point their MX (mail exchange) record toward a server, and the server could then be overwhelmed by mail its administrators didn’t ask for and don’t want.
Got any other questions about bounce messages and what they mean? Feel free to contact me, and I’ll do what I can to help.