Question : Problems recieving email to Entourage outside exchange network

A couple of nights ago, an outside company who helps me with my firewall and I had went into my firewall and change a configuration to the code.  The code from the access list was originally saying that anything coming into my exchange was allowed through and bypassing my spam service completely which there was no mention of.  We then recieved an IP block from my spam filtering company in which I had to go back into my firewall and change the access list to say we only allow inbound traffic directly from the spam company that gave us the IP block and then it goes directly to my exchange.  Well, since then, we have noticed a decrease of spam which is good but there are a couple of my users having issues.  I have 4 remote MAC users located in NY, 2 of which are using Office 2008 and are working just fine on sending and recieving.  The other 2 have Office 2004 for MAC and use Entourage and they can send email ok beause there send settings are configured to go through there ISP company but they are set to recieve from my exchange server using POP3, same as the other 2 which are working fine.  They, apparently are not able to connnect to my exchange and recieve this error when choosing sending & recieving from Entourage:

"The Server May be down, overloaded, or there may be too much net traffic"

I have talked with my company that helped me change the code to the firewall and they are uncertain how 2 users that have MACs are able to work fine but the other 2 are not able to recieve, same with my SPAM filtering service.  I dont want to remove that code we added to the firewall because it seems to be working.  Are there any suggestions on what i can do to try and get this fixed for them.  I have checked there accounts in AD and they are fine and not locked out, they have POP3 enabled, my POP3 service is working, i have rebooted exchange, i have checked the event viewer which is giving me nothing on this error, etc.  Any assistance will be appreciate, thanks!

Answer : Problems recieving email to Entourage outside exchange network

In System Manager select:

Servers > YourServer > Protocols > SMTP

Right-click the Default SMTP server and select Properties.
Click the Access tab.
Click the Connection button.
Click the Add button.
Select the option for Group of Computers
Enter 64.18.0.0 for the Subnet Address and 255.255.240.0 for the subnet mask.
Apply all changes and you are done.

The only considerations you have now are any devices on the network that require access to the SMTP server will also need to be added here as well (large printers with FAX capabilities, etc.).