BES 5 - periodically stops allowing users to send emails

[mlb]

We use BES express 5, and periodically the users will stop being able to send emails. They continue to receive them, but when they try to send they get the red X. A reboot of the server and they can send again. Any ideas as to what may cause this? I can't find much info regarding this specific issue.

[RTakacs]

If rebooting the server works then it could be one of the services crashing...
Is the BES on the e-mail server or on another machine?
Does emailing stop on outlook aswell when this happens or just on the device?

[MobileMadness002]

I would also like to know if it happens at consistent times throughout the day. IE, 90% of the time it happens @ 4:00pm or is it totally random? Does it happen to all USERS or just high traffic users or just random users? Since they are able to receive I can only assume that the majority of the BES services are still functioning. The issue is odd for sure. Do either the BESx, Exchange or Windows logs show any critical errors around the times the "X"'s appear on the devices? When they are unable to send, do the calenders continue to sync?

Disclaimer, I am not BES certified in any fashion, I am merely looking at all angles.

I just noticed, this thread to be almost 2 weeks old. I can imagine his users are getting frustrated if it is still occurring.

I wonder how much hair has been pulled out by now...