RCPT TO address

[highpointe]

OK. This is weird.

I have searched the forums for this error:

User unknown (in reply to RCPT TO command)

But none of the responses apply to my situation. When I am emailing to ANY address on a certain customers domain everything works fine until I attempt to add a ZIP attachment. When I add a ZIP attachment I get the above error. Any other attachment I can send, just not ZIPs.

I have Zimbra spam and AV turned off. Why is Zimbra still filtering it?

I.E. - text mail to susie@foo.com
NO ERROR

mail with jpg to susie@foo.com
NO ERROR

mail with ZIP attachment to susie@foo.com
User unknown (in reply to RCPT TO command)

Anyone have an idea why this is happening. I am at a loss.

Thanks!