That's odd because when I try to use the server command while the email field is empty, I get an error beep and the options dialog pops up and the cursor is in the email field. If I try to click the connect button in the options dialog while the email field is empty, I get an error beep and the cursor jumps to the email field. How much more does one need, a brick over the head? Just put an email address in there, if even a fake one because this is what the server uses for your username if it doesn't receive an ident response from you.
~ Edit ~
I just tried putting "" in the email field and disabling the identd and it worked fine, mIRC just used my main nick as the username...
-> <server.name> NICK RoCk
-> <server.name> USER RoCk "" "<server.name>" :rocko
RoCk is ~RoCk@xxxx-DA11F568.dhcp.xxxx.xx.xxxxxxx.com * rocko
