Mail filtering

Have you talked to AT&T about spam filtering? They may have a service you are not using. Most ISP's today can turn on spam filtering. This is the first thing to do.

If no, change your email to a hosting service that does offer spam filtering. There are many of those, and some offer outsourced Exchange services which may be just what you need. No need to have in house Exchange.

.... Thinkpads_User

We have the AT&T spam filtering on but we still get mail from fake email addresses. I recently lowered the spam filtering to 85 % to see if the website email would would go through but it still falls to junk mail.

You may need to look at its Blacklist and Whitelist capabilities to see if you can tune the filter. I have to do that with my mail suppliers. There is no automatic way for most of these things to work. Ask AT&T support how to manage these capabilities. .... Thinkpads_User

How many mailboxes do you have?

I have about 25 mailboxes

I will try your suggestion ThinkPads User

You may want to look at mail filtering service.  We do not use exchange server and use BlueHost for our domain hosting.  We set up a canit mail filter.  very easy to set up and works great. we have about 40 mail boxes.  You can also use their service if you do not want to set your own hardware up    

http://www.roaringpenguin.com/products