While a BU laptop can 'see' the BU servers(oncampus) it will use your current password. While it can not 'see' the BU servers(off campus) it will use the most recent password it has been able to see.
With a BU laptop setup to work with your BU name and password, it must be able to 'see' the BU servers when you are logging on in order to use your current email password. If you are on campus with the laptop, it can see the servers and will insist on using your current password.
The common scenario that comes up with a laptop though is if you change your password while you and the laptop are NOT on campus. When logging onto the laptop from off campus, it can not normally see past the BU firewall to find your current password, the laptop will then allow you to use the most recently known password that it is aware of. It will continue to do so until it once again can 'see' the BU servers and use the most current password.
There is one last trick that can be done off campus to see past the BU firewall, which is the BU VPN connector. If you connect to BU with the VPN connector, it creates a trusted connection to BU that can also 'see' the current password from the server. Thus, if you are able to attempt to login while off campus, and while having the BU VPN connection running, it can update the laptop to using the current password even while off campus.
Quick Steps to Sync Laptop Password
If you are off campus, the laptop password will be the same as the previous password. To sync the passwords, you can come on campus and it will automatically use your new password OR you can try the following:
1) login to FortiClient (the vpn)
2) press CTRL + ALT + DEL on the laptop and lock the screen
3) login and see if it will accept the new password