Gmail imposes a limit on the attachment size (20 MB) and the overall storage space (6 GB and growing) but there’s also a daily quote on sending email.  Break the rules and Google will disable you Gmail account temporarily without any warnings.

So while sending an email message to a large group of friends using Gmail, read the following rules to avoid temporary shut-down of Gmail:

Rule 1. If you access Gmail via POP or IMAP clients (like Microsoft Outlook), you can send an email message to a maximum of 100 people at a time. Cross the limit and your account will be disabled for a day with the error "550 5.4.5 Daily sending quota exceeded."

Rule 2. If you access Gmail from the browser, you may not address an email message to more than 500 people at a time. Try adding any more recipients in the To, CC or BCC field and your Gmail account will get probably disabled for 24-72 hours. Error: "Gmail Lockdown in Secton 4"

Rule 3. Always double check email addresses of recipients before hitting the Send button in Gmail. That’s because your account will get disabled if the email message contains a large number of non-existent or broken addresses (<25 ?) that bounce back on failed delivery.

Rule 4: This is slightly unrelated but still important – Google will disable your Gmail account permanently if you don’t check your Gmail email for a period of nine months. All the stored messages will be deleted and you Gmail address (user name) may be released for others to grab it.

Source:http://soft.aboter.com
Article:http://soft.aboter.com/post/rules-about-gmail-daily-limit.html