EMAILS NOT GETTING SAVED TO SENT FOLDER - I do not know if this will solve your problem, however, I have a Droid 2 Global that has been saving sent emails to the "Sent" folder just fine since March of last year. A couple of days ago, it stopped saving sent emails. I called Verizon tech support and the only thing they could tell me to do was delete and re-enter the account, which would mean that I would lose ALL of my exisiting, saved and sent emails.
After getting off the phone to Verizon, I tried a few things, but then thought, what if there is a limit on either the number of emails or the size of the "Sent" folder. I noticed that even though I had set the account to delete emails that were older than 30 days, it had never deleted any from the "Sent" folder. I had emails going all the way back to the day I got the phone. I deleted all sent emails up until the last 60 days and then sent a test email. It still did not work. Then I power cycled the phone and sent a test email and IT WORKED!!!
Apparently, there is some sort of limit on the "Sent" folder. I informed Verizon tech support what I had done so that they could add it to their troubleshooting list. Unfortunately, they do not have any documentation on such a limit, but promised to check with the Manufacturer to add it to their list as well.