Most of the host restrict to send emails to many users. But you want to send email to all users. Here Front End PM PRO has two very useful options.

Sending Interval: You can set interval of send email for announcement emails.

Emails send per interval: How many announcement emails will be sent per interval

Example: You set Sending Interval = 60 and Emails send per interval=100. So in every 60 minutes announcement email will be sent to 100 users.

 
Version 5.1 or more you can see how many emails already sent by go to Dashboard > Front End PM PRO > All Announcements

Screenshots: