This 2 settings are applicable only when you send an announcements or send a message with recipients are more than 5.

For example: for the setting: “Email sending interval” 5 min; “Emails send per interval” 10
when you send an announcement/message which have 100 recipients.

That means it will send 10 emails every after 5 minutes until all 100 users get their email.

It is only for Emails which send to their email address. Messages is not affected by this settings. User can send message as they like and email notification which send to their email address may delay.

Some host reject emails if too many email is being sent within short time. That’s why this settings is so that admin can delay emails a little bit to overcome this issue.