Comments on: Email looping between exchange server and isp

By: jimtrouble

jimtrouble — Wed, 30 Aug 2006 05:55:28 +0000

Thanks for all your replies!

Our ISP holds our MX records. They provide our spam filtering and virus checking services for our mail as well.
They have a filter in place that drops any email that doesnt match a certain criteria and destined for a specific domain (eg. 1stinitial.lastname@abc.com)

We have recently disbanded an exchange 5.5 server and now all internet mail is routed thro the new ex 2003 server. The firewall has been adjusted accordingly.
The external dns servers on our smtp virtual server are set as our ISP’s DNS servers and it is configured to use the dns name of our isp as a smart host.

Filter recipients who are not in the Directory” has been checked. Should i disable this?

Thanks

By: aalborz43

aalborz43 — Tue, 29 Aug 2006 17:09:14 +0000

Serendipity,
IMHO Filtering box should not be checked. According to Microsoft:
“Enabling this check box can potentially allow senders of unsolicited commercial e-mail to discover valid e-mail addresses in your Exchange organization, because during the SMTP session, the SMTP virtual server sends different responses for valid and invalid recipients.”

I think the problem could be on your ISP end, where they have enabled accepting (and forwarding) any emails sent to any address @yourdomain.com. They would need to turn that off.

At any rate, since they DO hold MX records AND route your emails, they need to come up with a technically better answer as to why they think the problem is at your end and not theirs.

By: serendipity

serendipity — Tue, 29 Aug 2006 15:53:38 +0000

In the Exchange Global Settings, Message Delivery properties, Recipient Filtering tab, you can check the check box labeled “Filter recipients who are not in the Directory.”