In Game chat deletes email addresses

[DUSTY1]

My alliance uses a graphical chat app so we can teach players the game. This necessitates me asking players for their email in the DomiNation in-game chat box. Why does dominations keep deleting email addresses from chat? Is this a safety feature? I even had them space the address out, like: DUSTY1 @ hopmail . com
It still gets deleted after a bit.
If there are rules of the chat (other than profanity and such) I would like to know. Thanks.