email limit per day gmail

1. Limit send mail per hour : 

you can use gmail smtp for max 90 users at a time else your gmail will be banned by google. So, to play safe you may send 50 emails per hour.

2. Limit send mail per day : 

To keep our systems healthy and your accounts safe, Google Apps limits the amount of mail a user can send. The limits restrict the number of messages sent per day and the number of recipients per message. After reaching one of these limits, a user cannot send new messages but can still access his or her account and receive incoming email.
The following peak limits apply to Google Apps for Business or Education editions and users in trial domains:

Limit type	Description	Business/ Education editions	Trial users
Messages per day	Daily sending limit*	2000	500
Messages auto-forwarded	Messages automatically forwarded from another account; not included in the daily sending limit	10,000	10,000
Auto-forward mail filters	Account filters that automatically forward mail	20	20
Recipients per message	Addresses in the To, Cc, and Bccfields of a single email*	2000 (500 external)	2000 (500 external)
Recipients per message (sent via SMTP by POPor IMAP users)	Addresses in the To, Cc, and Bccfields of a single email*	99	99
Total recipients per day	Individual addresses count in every mail sent; 5 emails sent to 10 addresses count as 50 recipients*	10,000	10,000
External recipients per day	Email addresses outside your primary domain, including domain aliases and alternate domains	3000	3000
Unique recipients per day	Individual addresses count once a day; 5 emails sent to 10 addresses count as 10 unique recipients*	3000 (2000 external)	3000 (500 external)

*applies to both internal and external recipients
The value of these limits may change without notice in order to protect Google’s infrastructure. Limits per day are applied over a rolling 24-hour period (rather than a set time of day).
If your domain has fewer than six users, it may take several billing cycles to reach peak limits.

3. Spamming Email :

- if in sending out your messages you create a sizeable number of 'undeliverable' ones, then Google may consider you to be spamming, and will lock your account.

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