When a new message is posted to the forums, some subscribed users are not receiving email notifications.
This FAQ assumes you have otherwise properly setup your Email Services and have made sure these are fully functional. Consult related Email FAQs here, your Sysop Documention, and your "Non-Programmer's Guide to Web Crossing" first!
This is usually due to a misunderstanding of how Email Notifications work. If your site provides "Email notification via links back to the conference", then this will be the default setting for all users when they subscribe via "Email" (versus Email Digest). In this case users receive links back to the forum and notification that a post has been made, but must visit the forum to read the new messages. Users will not receive further notification until they have visited the forum and read the unread messages. This prevents spamming people with notification messages before they are ready to visit.
If users wish to receive an email notification at all times, then they need to choose the "For your email subscriptions, send full email messages" option in their Preferences (providing your site offers that option).
Tip: if someone is new to your site and subscribes to an area (or the whole site), then EVERYTHING is new to them and so no new notifications will go out! They simply need to get caught up (Preferences "Mark subscription list as current (as if all new messages had been read).
If you are running our unsupported version 4.1, be sure you have updated/upgraded to the last 4.1 build for your platofrm. Builds from August 12, 2002 on have fixed an MX lookup problem that could sometimes cause the outgoing mail queue to hang up, and could also prevent changed DNS entries for an MX address to be picked up in a reasonable time. You can look at your Email Status page to see if it is full of outgoing emails.