Cannot use IceDrive Email address to join the Forum

Hi there, just wondering why we are not able to use our IceDrive account email to sign up to this forum.

I tried to do this, but told i cannot use my primary email address.

Cheers

I guess for security reasons. If I understand correctly, the forum is developed/managed by a third party (discourse.org?), in which case Icedrive might not have complete control over its security.