OK, The scenerio is as follows...
A small business with 10 computers; Six PCs running XP SP3 and four Macs. The PCs are using Outlook 2003 to retrieve email and the Macs are using whatever built in client comes with them.
All of them are connected to a server running SBS 2003 Premium.
They have a website on an ISP other than the one they get their internet from that provides special services and hosts their POP3 e-mail. For the purposes of this question we'll say that the site is called www.mycompany.com and I'll refer to the provider as ISP-2.
Rather than using the SBS 2003 built-in Exchange server, they just had their Outlook clients configured to get e-mail directly from ISP-2. The POP3 e-mail delivered by ISP-2 has a "deliver and delete" policy because e-mail is a free service they throw in as part of a larger bundle this company purchased. So if a client gets munged in any way, that e-mail is gone forever, which naturally concerned me. Besides missing out on all of the protection and redundancy that Exchange provides, they're also unable to use any of the Exchange features intergrated into the internal website.
Naturally I wanted to convince them to switch over to Exchange exclusively, but that would entail buying Exchange clients that run on Macs. Which is not an expense they're eager to shell out, because the recession has hit them pretty hard. Also, although it may in fact be easy as pie, I would have no idea how to install or support such products on Macs, since the last time I touched one was back in 1987.
So I went ahead and configured the POP3 Connector that comes with SBS for them. I created accounts for all the PC users and I just left the Macs to fend for themselves as SecureNAT clients behind the ISA 2004 firewall.
Everything seemed to be working fine. Everyone could send and recieve email to and from external sources. I figured my job was done.
But then they called me saying that they couldn't send email to each other within the network. Since the POP3 connector on the Exchange server was collecting email for the six PC users, I had removed all of the POP3 account information from all of the Outlook clients.
I tried a great many things, but what eventually worked for the PC users was to add their POP3 accounts back into Outlook, leaving the Exchange accounts as the default accounts, and keeping the POP3 accounts as secondary. Then I went to the Send/Recieve settings and unchecked "Send mail items" from the Exchange accounts and unchecked "Recieve mail items" from the POP3 accounts. So incoming mail would be collected by the POP3 Connector on the server and delivered to the Echange accounts and outgoing mail would be sent from the POP3 clients.
Again, everything appeared to be working fine and the PC users could email each other and had access to all of the Exchange and companyweb features. I figured my job was done.
But they called again saying that they couldn't send e-mail to the people using Macs. I had them forward me the failure message....
"Your message did not reach some or all of the intended recipients" - "The e-mail account does not exist at the organization this message was sent to"
So logged into the server via VPN, RDP'd to the server desktop as the administrator and from there connected to a PC client using Remote Assistance. I sent some test e-mails and got the same result they did. "The e-mail account does not exist". But of course they do exist because the Macs are still receiving email from outside the network just fine.
I tried making the POP3 account on the Outlook clients the default and the failure messages stopped. We couldn't confirm that they were actually recieved because the Mac users had gone home by then and the owner knew less about Macs than I did. But after testing email to and from serveral internal and external sources with no problem, I figured we must have it licked now.
But then the owner calls me back saying he's still getting the failure message when he tries to e-mail the Macs. I log in again, no failure messages, I log out and they return. And yes, I checked his sent mail to confirm that we were both sending to the same addresses.
So now I'm totally stumped. No failure message when I'm sending from his account via RA, but as soon as I end the session they start happening again.
Is this some weird manifestation of Heisenberg's Uncertainty Principle? Has Hell frozen over? Or does God hate me?
At my wits end.