email bounce backs

Hi,
I finally got OWA back up and running. Now I have another problem.
Since we set up a T1, some users are saying that email recipients are unable to respond to their emails.
I went into Exchange server, to have a look. the only thing that was weird was that the primary SMTP address was reset to another alias. I went and manually changed all addresses to the correct address, but when I went back to check them, they had reset themselves back again, within 2 minutes........


Also, this is weird. When switching the data line over to T1, the WAN connection would not stay "constant". the connected light was blinking, and we could not get it up and running. So, after having the network down for 1/2 a day, we surmised that the network slot on the motherboard is bad, and we bypassed it with a USB NIC card. the weird thing is that we had had no problems with the existing NIC card. We tried a brand new one, but that did not work either.........