We just sent a mass email with the correct body message, but incorrect subject line. Is there a way to recall the emails that we sent with the wrong subject and then resend them with the proper subject line?
There is no such thing actually, when a message is sent it completely escapes from your control. It will travel thru the internet from your mail server to the recipient mail server until it is finally fetched by the latter. This is not something that depends on our software, it is how the internet emailing system works. MaxBulk Mailer delivers messages exactly the same way as any other e-mail software.
Indeed once your server accepts your message for delivery, it becomes the unique responsible for its routing till its final destination. In other words, the mail server receives your message, if everything is correct it tells MaxBulk Mailer it is valid, the server accepts your message for delivery and close the connection. At this point MaxBulk Mailer is done. No way to undo.