I have FIOS and the actiontec router. I can't send emails vie the M1EXP. It's very frustrating. I have not seen any workarounds posted here. This thread describes the problem but workarounds were false alarms.
OK. Here's an update on where this issue stands.
First I would like to thank everyone here who has replied or provided suggestions. Special thanks to Dan who pointed me down the path to get the right info to Elk.
I just completed a conference call with Elk's M1XEP engineer, and he has a high level of confidence that what we are seeing is indeed the same problem that existed with the actiontec router. This is the first that Elk has heard of the westell router that is now being used in new fios installations. They will need to explore their options as to what the possible fixes / workarounds are and proceed from there. What, when, how fast, and whether they are able to provide a solution, is clearly at Elk's discretion. But at this time if you are looking at the combination of the M1XEP and FIOS with the westell, it is problematic. The only work around known at the moment is to run a SMTP proxy on a PC attached to the local LAN, or provide your own router, which can create problems with FIOS. I happen to have an actiontec, so I will probably try to go back to that while I wait to see if Elk comes up with anything.
Let me say that my decision to go with the Elk has only been bolstered by this event. The support and attitudes of the personnel at Elk has been exceptional. I thank them all.