I have been conducting a test with my phone for the past 3 days to verify my findings on the email client built into the Android OS. The main thing I have been look at is I noticed that when i connected to Wi-Fi, I had connection issues with email locking up and not checking for new emails (not getting notifications). So, for the past 3 days I have turned off the Wi-Fi on my phone to see if this might help. So far i can say that I have not had any problems with getting new emails over my POP3 accounts. I wanted to test this out for a week, but I figured I would give you all the information to what others are able to get from this experiment and to and see if this fixes the problem for others as well.
I do have issues with signal as well, especially with where I work, but this has not been an issue. Actually, it seems as if the signals are now not interfering with each other as much and I have been able to get a stronger 3G signal where I had none before. The stronger signal might also not be true, as before I turned off the Wi-Fi, it might of been getting a better signal here.
I would encourage anyone to test this and report back to this thread and let others know how your test went. I will do the same in a week. So far so good and I am getting continual updates for email!
Edit: added the word notifications to make it easier for searching