Zoho docs - trying to invite someone to share a workspace. their email address has a - in it

Zoho docs - trying to invite someone to share a workspace. their email address has a - in it

Hi
I wanted to try out sharing a workspace with someone else. Her email address has the - in the domain name. I get a message telling me that "special characters are not allowed". But her email address is completely valid.

Is this correct? You cannot have a - in an email address?
Thanks
Lesley