spammers targetting our server

[bhwong]

Hi,

We have over 100k of spam emails send from our Zimbra. It appears that our Zimbra is acting as a relay for external domain users. What settings can we use to only allow domains hosted in Zimbra to send out emails?

Also, many valid emails get blocked when I enable Protocol and DNS check. Which of the 6 checks are recommended that will not affect valid emails?

1. Hostname in greeting violates RFC (reject_invalid_hostname)
2. Client must greet with a fully qualified hostname (reject_non_fqdn_hostname)
3. Sender address must be fully qualified (reject_non_fqdn_sender)
4. Client's IP address (reject_unknown_client)
5. Hostname in greeting (reject_unknown_hostname)
6. Sender's domain (reject_unknown_sender_domain)

[phoenix]

Originally Posted by bhwong

We have over 100k of spam emails send from our Zimbra. It appears that our Zimbra is acting as a relay for external domain users. What settings can we use to only allow domains hosted in Zimbra to send out emails?

I've already answered this question yesterday in your other thread, Zimbra does not act as an open relay by default. Unless you've modified the configuration Zimbra will not allow mail to be relayed through your server. You need to look in your log files at some of the exact errors and traffic that you see to determine what the cause of your problem is.

Merely saying that your server is a 'relay' without any evidence makes it impossible to advise you. You should also look at some of the ant-spam tuning techniques in the wiki and search the forums for further details of anti-spam improvements.

[bhwong]

Sorry, I didn't see your reply in the other thread. I have done open relay test and have passed it. My question is, why is there thousands of emails in our Zimbra deferred queue that are sending from external domain to external domain?

[phoenix]

Originally Posted by bhwong

Sorry, I didn't see your reply in the other thread. I have done open relay test and have passed it. My question is, why is there thousands of emails in our Zimbra deferred queue that are sending from external domain to external domain?

I'll say it again, you need to look in the log files to determine what the exact problem is and why those emails are there.