Error: has exceeded the max emails per hour allowed. Message discarded.

Issue :

While sending out mails during a mail campaign , the following error occurred :

has exceeded the max emails per hour (300) allowed. Message discarded.

Fix :

If you are using a cPanel/WHM server,

1.Log into WHM
2. Go to Main >> Server Configuration >> Tweak Settings
3. You will see an option like “The maximum each domain can send out per hour” . Set it to the number you want. If you set it to 0, it is unlimited .

OR

You can SSH into your server and edit the file /var/cpanel/maxemails (which doesn’t exist) and add domain=number pairs for those that you want to restrict (or increase) to a particular number of emails per hour.
e.g:

somedomain.com=100