E-mail limits
From the beginning, salesforce.com has made it clear that they do not want their name associated with spam in any way. For this reason, there have always been limits on the number of mass e-mails you can send from the Salesforce1 Platform. However, a user can always send as many single e-mail messages (which can have multiple To, CC, and BCC recipients) as they can via the standard e-mail interface in the Salesforce GUI.
The mass e-mail limits vary based on the edition of your subscription. They are calculated in a rolling 24-hour period. This means that once you have sent the maximum number of mass e-mails allowed, you will have to wait a maximum of 24 hours before you can send more mass e-mails.
Apex includes the ability to send both single or mass e-mail messages. But since Apex can be used to programmatically send multiple single e-mail messages, the Salesforce1 Platform counts e-mail messages sent via Apex in your daily limit. Remember, the people behind Apex are very innovative...