If I remember correctly, the "disallow 3rd party mail services" option blocks mail FROM a BIS account, but doesn't block the receipt of messages TO a BIS account that someone has set up previously on a device. I suspect that you'd want to set the device-side firewall (available from 4.1 of the handheld OS if memory serves) or talk to your carrier to disable BIS on your SIMs if appropriate / possible.
|