I have a membership database in which the email address is used as the
unique field for reference purposes.

I run a query that seeks to remove email addresses from a mailing list
if they do not appear in the database.

I need one address to be in the mailing list which is not a member
email address.

I have a query which links the email addresses and seeks the "null"
entries in the database and then deletes them from the mailing list.

I have been using this as a criteria:

Is Null And <>"username@aaa.com"

to prevent "username@aaa.com" being deleted and it has been working
for months. Suddenly there are no records in the query in spite of the
fact that if I reduce the criteria to "Is Null" the are eight
including "username@aaa.com".

I am baffled.

Where do I look next?

Thanks,

Robin Chapple