An issue that pops up often is when sending messages from GMail, they appear in the BB Inbox.
To try and settle this, create a filter for your gMail account on your carrier's BIS site:
Filter Name: Your choice
Apply Filter: "From" Field
Contains: youremailaddress @ gmail.com
Also make sure to select "Do Not Forward Messages To Device.
In case you don't recall the BIS site for your carrier,
this link includes links to just about every US carrier's BIS sites.
While in BIS, also edit the setup to eliminate the Auto BCC option if present.
SteveTaz