The idea behind such messages is to trick a reputable mail server to re-send a spam message (as part of the non-delivery notification) to the real recipient, placed in the reply-to header of the message. This rather common phenomena is known as backscatter.

/Rolf 

Hello,

I am just curious about a lot of messages to unknown recipients I see in logs.

I wonder if those messages can be redirected to a special user instead of being just rejected.

Thanks.

Have a look at this setting in MercuryS configuration:

Accept mail for invalid local addresses

In regular use, MercuryS will refuse to accept any message that appears to be addressed to a local user who does not exist. This refusal can result in the sender getting unhelpful mail messages from their mail program. If you check this control, Mercury will accept the message and the Mercury core module will later reject it and send it back to the sender, but in a more clearly-explained form. Mercury will also refer a copy to the postmaster, who can then correct any addressing error and pass it on to the proper recipient.

/Rolf 

Hello,

Thanks for your reply.

I have already tried this solution but this parameter is unrelated with my question. It simply sends a message to the sender, real or fake, about the recipient doesn't exist.

What I want to do is to catch the e-mail.

Thanks again.

Well, you will get a copy of the message to the admin account, and you can stop all delivery failure notifications by emptying the field for Delivery failure template in the Files tab of Mercury core configuration. However, this would introduce a risk that legitimate senders that make a small error in the address would presume that the message has been received in good order while it in fact was never delivered, so I can't really recommend it.

It might be possible to create more appropriate behavior without stopping all notifications, depending on what you actually want to do here, by using filtering rules or by writing a deamon, though.

/Rolf 

It's just curiosity. I was wondering what sort of spams are being sent to obviously unexisting recipients just to get an error message. And when I say unexisting I mean bcggbphxwb@mydomain.com (this is a real example from 1 minute ago).

Anyway, thank you very much for your help.