Put this in Cell D1:
=IF(ISBLANK(B1),A1&C1,A1&B1&C1)
Add & " " & between Cells if you want spaces
HTH

Die_Another_Day

wrote:
Excel MVPs:

So this is another question about figuring out emails. I have first
name in column A, Middle Initial in Column B, and Last Name in Column
C, and Domain in Column D. I need a formula that gives A.B.C@D If there
is a middle initial, and A.C@D if there isnt one. Thanks again.

Reece