By default, Exchange creates email addresses based on the default smtp domain name and username.  If you want to customize email addresses, you can set the recipient policy to do so automatically, using special variables.  This can come in handy if you need to add a secondary domain address or if you wish to have custom emails such as firstname.lastname@company.c0m.

The variables that Exchange supports are:
%g  = givenName (First Name)
%s  = surName (Last Name)
%4s = the integer corresponds to the number of letters of surname
%d  = displayname
%m  = Exchange alias

For example, let’s say that my default exchange policy is only configured with my smtp domain name and my username is cfriday, my email by default would be cfriday@fridayfarm.c0m.  However, if I update the default smtp address to be %g.%s@fridayfarm.com, my email would now be carson.friday@fridayfarm.c0m.

I am in no way endorsing microsoft exchange, just giving some advice on how to make it suck less…