The key thing to remember here is that when someone makes an email address change in online banking or CU*BASE, we send an email notification of this change to both the old and the new email address as a security precaution.  Therefore, it may not be enough to simply look for accounts that have the email address of the member attached.  The best method of attack to solve this type of question is to use Tool #100 "CU*BASE Report Builder (Query)."  Query the appropriate month's maintenance file (either CUFMNT or ECUMMYY) using the critieria shown below:

          MNTOLD    LIKE = Contains the Pattern Of    '%sentemailaddr%'
OR    MNTNEW    LIKE = Contains the Pattern Of    '%sentemailaddr%'

Two key things to remember:

1.  This is case sensitive.  If you don't find it in lowercase, try uppercase and mixed case.
2.  Use the like pattern with wildcards (%) and leave out the last part of the email "@gmail.com."

Doing it this way makes it less likely that you will exclude the information you really need from your query results by accident.