Invalid email format for admin user

[robroymedia]

Hello folks,

praise the MAX guys, fantastic job, installed with no problems whatsoever. Tiny little problem though and can't figure it out (probably because I don't know where to look!). When I add a new administrator user in the admin section I get "invalid email format, add user failed". I suspect it's because the first part of the email address is the following format - rob.callan@mydomain.co.uk - the period is being classed as an invalid character, if I enter robcallan@mydomain.co.uk it works fine, but obviously the password email will not get to the user as the address doesn't exist!

Any clues where to look to rectify this problem as there are alot of emails out there containing a period in the first part.

Thanks in advance.