They intentionally don’t say “this is spam” to avoid giving spammers any clue about how to bypass the filters. If your message looks like spam to the recipient’s email server, “mailbox unavailable” is one way servers reject your message. The account could remain suspended indefinitely, or things could return to normal once your recipient regains access to it. This might mean your recipient was doing something they shouldn’t have, but more often it means the account was hacked and taken over by someone using it to send spam. It’s possible the account was suspended due to abuse. Make sure you’re not only entering the address correctly, but that it’s the correct email address for whomever you’re trying to reach. This is a variation of the preceding item: it’s possible the email address you’re sending to may have been valid at one time but has since been closed.
This is perhaps the most common cause of “mailbox unavailable”. Any error could have you sending to a non-existent account, which could easily result in this error. I can’t even be sure I’ve listed all the reasons you might get this error message, but these are the most common.įirst things first: make absolutely certain you’ve entered the email address correctly. I can’t say which of these might be the cause in your situation. So whatever might cause a “mailbox unavailable” on one system might generate a completely different message from another.Īll we can do is make some guesses. Unless there’s additional text in the error message saying more - which there typically isn’t - there’s just no way to know exactly why it failed.ĭifferent mail systems use different error texts to report the same errors. The only thing it tells you is that the mail could not be delivered. “Mailbox unavailable” is a frustratingly vague message.
The “mailbox unavailable” error is the email equivalent of saying, “Something didn’t work”. Unless there’s more information included with the message, there’s rarely any way to get more details. “Mailbox unavailable” can indicate that your email message failed to deliver for any number of different reasons, ranging from bad email addresses to closed or suspended accounts to quotas having been reached to mail server problems and more.