Some email comes to my BB and some does not

From BlackBerryFAQ

IF you are using Outlook to download your email to your desktop PC, Outlook is likely "deleting" mail from your email server when it downloads it to your PC.

There is a setting in Outlook to "Leave Messages on Server".

For MS Outlook 2003:

Outlook > Tools > Email accounts > View or Change existing > next.

Highlight the email account > Change > More Settings.

Advanced Tab > Leave a Copy Messages on Server

Check that box.

• You will need to perform this edit for each Outlook email account you have.

Other versions of Outlook have a similar setting although it might located in a slightly different location in the :advanced settings"