Issues Receiving Mail After Brief Connection Loss

Ok, we've been having a ton of problems at our office with our Verizon DSL connection. Verizon tech support has been less than helpful. Their big solution was to downgrade our connection speed to 1.5 Mbps try to maintain a more stable connection, since we are almost the max distance away from their central station, and evidently are on a fairly noisy line. This did not work, even when we were supplied with a new modem. Before this recent issue, we hadn't really had any connection problems in about a year.

Our internet connection continues to drop for short periods. The big issue is, when it comes back, we have access to the internet, and our SBS 2003 server's web functions (OWA, RWW, SharePoint) can be reached from the internet, but inbound connections to our SMTP virtual server time out. The only way to open email back up is to reboot our WatchGuard FireBox (hardware firewall) through its configuration page. This will restore email delivery until our next drop, after which, I will need to restart the FireBox again, and it goes on and on in this fashion.

Any thoughts? Is the Firebox possibily going bad? If that was the case, wouldn't we have issues with more than just email after the connection was restored?