I want to application or script

we use gmail to send letters to companies and maximum limit of gamail is 400 letters daily and such procedures cause me meny problems as we send them together although i have many emails i use to send to companies which are more than 100 email i nedd any thing which might help using gmail application without openeing the email itself not to wast time and to prevent gmail to become disable as they think that this way of sending emails is spam way although i send to registered companies i need to load many emails at the same time and also remote time of sending to give chance to emails to reach one gradually as i may need to send 50 or 100 emails at the same time for every email i add because i may add many accounts i have 300 hundred emails and i open them daily to send to companies as i have 50000 company and gmail send 450 letter for every email and this is difficult to open all the 300 emails every day and i want just to add all of them and send every day with one click from the number of emails i need wether i want to send from 100 email or fromm all of them do you have anything which might help