I only see two or three entries in a day for

"... was returned to sender - The following recipients are unknown: ..."

Meanwhile hundreds of emails to bogus email addresses appear to get sent to my servers each day.  When and does SpamFilter validate the recipient email address and are my results normal?   Is there something special needed to support this on my receiving email servers?

Thanks.

Thanks. The symptom I'm having is that SpamFilter is not logging this unless the receiving SMTP server returns a 550 SMTP error.  

If the receiver issues a "550" or "unknown user" error SpamFilter correctly writes two log entries (there are two):

...Some recipients do not exist, sending NDR bounce to sender

and

EMail from: whateversender@domain.com to: invalidrecipient @otherdomain.com was returned to sender - The following recipients are unknown: invalidrecipient@otherdomain.com 

If the receiving SMTP server responds with anything else the NDR is sent correctly but nothing is logged by SpamFilter.  For example, when my server rejects the rcpt to: command with a 501 5.5.4 Invalid Address the NDR is sent, but nothing logged by SpamFilter

It appears that SpamFilter only logs this event properly when a SPECIFIC error code is given to it from the receiver.  SpamFilter SHOULD log this when ANY 500 series or permanent error is given on the rcpt to: SMTP command by the receiver.

This is important so that we know which recipients were not delivered by reviewing the logs.

Thanks again.

Email me your Public IP so I can add to our list of allowed IP connections.