<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Kremmen:
If we make our profile email address invisible to others, there is nowhere else in the profile to put the "user at domain dot com" version that isn't intrusive. (... basically, the sig and interests which print on every single post are the only free text fields available.)</font>
That is exactly what Dan means. If you do not wish your email to be available do not make the valid email address publicly available. That means giving your email in an altered form in the signature field or in the body of a message. You are correct in believing that you must give a valid email address to the UBB system itself.
Well behaved bots will obey the directives in the robots instruction file that Dan created -- however as you must know spammers do not really care about being well behaved.