reasons why emails bounce back

Several weeks ago I had a client call me in a panic. She said that her emails were bouncing back and could I fix it? It ended up that she had just sent a big mailing with attachments out and a handful of the emails bounced back. Her bounced emails inspired this blog post.

There are any number of reasons why emails might bounce back. What is certain, is that when they bounce back, the server that bounced them will give you a reason why they bounced, right at the top of the bounced message. Usually they bounce for benign reasons that have nothing to do with who hosts your email.

For example:

You may be sending the recipient an attachment that is too large for their mailbox capacity. If that happen, there will be some text that states that the message size exceeded the fixed maximum message size. (see image below).

It could be that the email address is no longer valid, or has a typo in it. If this is the case, you will get a message saying that the address was rejected or that the recipient is not their customer or doesn’t exist.

See the two examples below:

It could be that the mailbox of the recipient has reached its quota or is full.

Often, the receiving person’s mail server is down or has a very large queue. When that is the case you will receive a message at the top saying that the email hasn’t been delivered yet, but your server will try again.

If your mail server has been blacklisted for spamming, then your email might bounce back as well. In that case there will be a clear message stating so.

If I am hosting your email, and you get a message about RBL lists and black lists, then please DO contact me immediately, forward me the bounced email and I will put the wheels in motion to fix the situation.

Can you think of other reasons why emails bounce? and what the clues are in the returned mail heading?

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