Verify Send filtering?

[Gotenks]

Hi,

We have problems with too much spam sending through our Exchange relay internally. So in a bid to stop that we're trying out Proxmox mail gateway.
I installed Proxmox Mail Gateway in trial mode and put my Exchange 2010 server's Send connector to only point to proxmox. Then adjusted the proxmox send connector to port 26, went back into the send connector and made sure EHLO HELO requests are made in the correct name.

How do I make sure outbound messages are being blocked?
I went to Administration > Tracking Center > Realtime and see:

Aug 28 18:58:22	smtp	15798	D44859C7AA: to=<norxftjjdyafb@aleslahweb.org>, relay=none, delay=23052, delays=23035/0.06/17/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=aleslahweb.org type=MX: Host not found, try again)
Aug 28 18:58:22	smtp	15799	64BC59C79E: to=<shilaloida@homesweb.com>, relay=none, delay=23052, delays=23035/0.07/17/0, dsn=4.4.3, status=deferred (Host or domain name not found. Name service error for name=homesweb.com type=MX: Host not found, try again)

Then I go to Administration > Queues. I see several domains with messages waiting to send. Here is one example:

Sun Aug 28	12:34:11	11	MAILER-DAEMON	shilaloida@homesweb.com
SMTP RESULT: Host or domain name not found. Name service error for name=homesweb.com type=MX: Host not found, try again

That must be spam, but I'm not sure if it should be in a queue repeatedly trying to send?
I go to Configuration > Mail Proxy > Default Relay... Changed it from my routers local IP to the Exchange box but not getting any change. Says SMTP port is 25, should be okay for the port.

I just don't know why the queue is piling up in proxmox and it's worrying me.

 

[Gotenks]

Administration > Queues > Flushed queues (not sure what that does but... just spam was in the folder), delete all messages.
Nothing has been in the queue all day. Changing Default Relay from gateway/router IP to the Exchange server might've done it.