[Marco van Herwaarden]

I know it has been discussed before recently, not sure if a hack was made.

I doubt however that the reason given above by your users is a very valid one. It is easier to access a board then to access a mail server. So unless you got a lot of protections setup on your board (like only allowing certain IP-addresses), the above is not a very good reason.

There can ofcourse be other more valid reason for your users to want this, the question however should be: Do you as a board owner want to have members that don't visit your board (and therefor also not participating).