E-Mail notifications and Mail Queue
In each plugin you can select if users will be able to subscribe to comment notifications on new comments. You are also able to set moderators groups that will also receive emails on new comments. Depending on how many people need to be notified the notification process can take long time. In the past comments were sent immediatly after the comment was posted, which lead to a long wait time for the user that made the comment. His comment was not shown as save untill all emails were sent. Now per default we sent maximum of 5 e-mails on page load. This will be fine for most websites, but if you have a high volume of people on your website & a lot of users that are commenting it will be way better if you setup a cronjob that will sent the comments.
On the mail queue tab you can see the URL for the cronjob.
If you have a lot of users that comment on comments and if a lot of people need to be notified, then it can happen that emails about new comments get delayed a lot of time since the mail queue is long. The cronjob url has a parameter total=10 -> you can change it to a higher number in order for the cronjob to send more emails when it runs.For example if you set your cronjob to run each 5 minutes and the total parameter is set to 10, this means that a total of 120 emails can be sent per hour. If you need to send more you'll either have to set a lower time for the cronjob to run or you'll have to set a higher total for the emails to be processed at once.