Google Wiki:Gmail sending limit

If one sends too many emails, copies too many people, or gets too many bounces on the emails they send out, the user may find their Gmail account suspended for an unknown period of time. This is known as the Gmail sending limit.

This a is a common issue, with a lot of discussion occurring in the Gmail Help Discussion Group. The limit is placed in order to prevent abuse of the service, and to prevent spam.

What is the limit?
From Gmail Help on Sending limits:


 * 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 POP or IMAP 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.

The number of bounces (undelivered messages, as explained above) also have an effect.

What is the solution?
The most common suggestion is to use Google Groups, or create a Google+ Community. These two services are designed to communicate with a large number of people, and can be much more effective than trying to use Gmail.

How long before I can send mail again?
The time has been known to vary. Most users who have experienced this error report 24 hours, though many say 24 to 48. Other users have reported periods of three to seven day outages. However, it is generally safe to say that the suspension will be removed after 24 hours.

Criticism
Many users have complained about this limit, specifically about Google's approach. Instead of giving a warning that a user is approaching a limit, Google immediately suspends the account.. Most users are not aware these limits exist.