anti-spam measure for invite emails: "Error: Sorry, links to specific websites are not allowed!"

[williamstein]

1. Invite another user to a project, and include an email address in the title of the project (hence the invite message).
2. See the error "Error: Sorry, links to specific websites are not allowed!"

This is an anti-spammers measure, but it is clearly going overboard.

• It shouldn't flag emails at all.
• It should be clearer about what is causing the problem.