Why does my Bold hold so few e-mails?

Currently my Bold 9900 receives e-mails from 2 accounts my personal and my business e-mail accounts. I have noticed lately that I only have 2 months worth of messages on hand even though I have over 5 gig of space available. Is there a setting that limits the number of e-mails or bytes ? I've looked everywhere and cannot find a related parameter / setting. I have pulled the battery 2 or 3 times in the last 6 months because the unit froze / did not respond. Does this dump old mail??

In your email settings there should be a area to select how long you want to sync