1 | if there are rows with the given string in any of its cell, else 0. |
With respect to the message list table in Evolution Mailer, the following call will return 1 if there is atleast one mail in the list with the given string in the subject field or sender field or in any other field for that matter.
doesrowexist ('dlgContactListMembers', 'tblContacts', 'Sample subject')