The Subscribe2 plugin uses an internal mail function to deliver emails to subscribers of a blog. It is therefore no great surprise that many issues raised by users involve missing emails.
Some of these emails do actually arrive but are blocked on client machines by spam filters.
Some of these emails are not sent, and rightly so, because the expected recipient has not actually subscribed (or subscribe correctly).
But, if both of these are not the case it may be down to the server configuration. Since WordPress is written so the Email function can be over ridden by a plugin there is now an excellent plugin called SMTP Plugin that may solve “No Email Received” problems by pushing emails through SMTP rather than a server email function that may be turned off or poorly configured.
If you are having problems with this email delivery plugin it is well worth a try! Note: You’ll have to edit the subscribe2.php file and replace instances of @mail with @wp_mail for this to work.