why did I get a Mailer-Daemon email....?

Why did I get a mailer-Daemon email telling me that there were no records of the email address who I sent an email to. The address in question is on my contacts list and I have used this same address for the person for many years, so no way could it be wrong or misspelt or any other reason they could come up with. All I did was forward the original email to the same email address and so far it hasn't been returned. So why was it done in the first place??

Ajaye, June 2013

The message mean that the e-mail address you used don't, or no longer, exist.

If the recipient of your message changed his address, for whatever reason, that address don't exist anymore.

It's possible, even remotely, that he violated the terms of service. This can result in his account been terminated.
Possible causes of termination by violation of terms:
Propagating chain e-mails.
Sending virus or malware infected material.
Cyber bulying.
Account used for any criminal purpose.
Account been highjacked and used for the above.

If his account got highjacked, it also probably terminated.

It's not impossible that your contact list got corrupted, maybe only 1 or 2 addresses affected. Carefully inspect your contact list for any possible error.

Lastly, there is an extremaly small possibility, less than 1 in 1 000 000 000 000 chance, that your message was not routed properly and ended up on the wrong server.

Electro, June 2013