Here is a trigger I had written to limit the quarantine to people that are actually checking it.  Basically it checks the DB when a line is inserted into the quarantine table and marks it to be deleted if there is not a corresponding user in the logins table.  It has saved me a ton of space for non-existent users, or users that don't check the quarantine.

IF (SELECT COUNT(*) FROM [dbo].[tblLogins], [inserted]
    WHERE [dbo].[tblLogins].[EMail] = [inserted].[EmailTo]) < 1
BEGIN
    UPDATE [dbo].[tblQuarantine]
        SET [Expire] = 1
        WHERE [QuarID] = @@IDENTITY
END

This is after an insert to the tblquarantine.  It has worked wonders for me.

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