1) Anytime there is a problem with e-mail on a Blackberry, have the user first check their internet service by surfing the internet. Most users will notice e-mail isn’t working before they notice any other data related service. Also note that text messaging uses the voice circuit, while e-mail and internet uses the data circuit. It is possible for one to work and not the other. This is a common problem is when a user roams out of the data coverage area for a length of time, and the blackberry sometimes has a problem detecting that it is back in data coverage.
2) If the internet is not working, have them power cycle the device by removing the battery. Frequently the “soft power down” from within the phone is not enough to reset the antenna and redetect the data circuit.
3) If the internet is still down, and they are in an area that usually works then have them contact their service provider.
4) If they are using a Blackberry server, and you’ve confirmed that the internet is working, then check the exchange and blackberry services
5) If they are using a IMAP for their e-mail, and you’ve confirmed that the internet is working, then you may need to re-register or “validate” the e-mail account (typically through a provider web portal). This happens when the mail server at the phone provider, which uses IMAP to connect to the users mail server and passes those messages along to the phone, looses connection for any length of time. (This can happen even if the mail server is 100% available – I have this problem with Sprint about 1-3 times per year).