Gmail
In an effort to fight spam and prevent abuse, Google will temporarily disable your account if you send messages to more than 500 recipients or if you send a large number of undeliverable messages. If you use a POP1 or IMAP2 client (Microsoft Outlook or Apple Mail, e.g.), you may only send a message to 100 people at a time. Your account should be re-enabled within 24 hours.
If you communicate with the same group of people on a regular basis, you might be interested in Google Groups.
Learn even more ways Google products work together.
If you send a large number of undeliverable messages, we suggest verifying your contacts' email addresses. It's also important that everyone you are sending mail to is willing to receive it.
Learn more about best practices for sending a large amount of mail through Gmail.
- POP: POP (Post office protocol) is a one-way download of your messages that allows you to access your mail with a mail program like Outlook Express or Apple Mail. POP only offers one-way communication, which means that actions you take in the mail program (like marking a message as read) won’t be synced to Gmail.
- IMAP: IMAP (Internet message access protocol) lets you download messages from Gmail so you can access your mail with a program like Outlook Express or Apple Mail. IMAP syncs the actions you take in Outlook Express or Apple Mail with Gmail so if you read a message in your mail client, it'll be marked as read in Gmail.