Ask mailer mailer.
The infrequency of mailings causes problems – I have a similair problem because often I just don’t get around to mailing.
People forget they know you and your mailings.
Always use the same name and make the topic the same or something recognizeable.
Do you have an email address set up that receive4s return mail? With mailermailer you likely do. This return mail should give you clues.
Also if you mail thursday or later, don’t worry about the stats until the following tuesday.