The Mass Mail policy covers mailings that go to more than 1000 individuals, other than self-subscribed mailing lists. If you are mailing to less than 1000 individuals, you can choose to use the Mass Mail service or you may distribute the messages yourself. 

Note: If you choose to distribute the message yourself, you can send to up to 1000 recipients; however, there is a limit of 500 recipients per email message.

You also need to obtain approval if sending to more than 1,000 recipients.  If you decide to send your own mailing, see Sending Your Own Large Mailings 

We discourage the sending of your own mailings because your account may get locked or the message blocked at the recipient address for sending too many messages.