Sometimes you will find your Gmail (Google mail) account locked and you will not be able to access it. This happens due to many issues.
Google or Gmail is a machine basically, it uses some algorithm to find out if you are a spammer. Spammers usually access Gmail using many software and they send emails to unknown address. So Google set a system where these things are blocked automatically.
1. If you are sending Bulk emails to your friends.
- You may want to announce some message to your friends or to all your contacts
- When you send an email more than 100 recipients, Gmail blocks your account
- When you send emails to a lot of undeliverable addresses, Gmail blocks your account
2. If you are logged into several computers or several browsers with the same ID
- You may have forgotten to sign out from other browsers or other computers
3. Using some software to automatically access your Gmail account
4. Bulk downloading of emails using POP or IMAP client
Above all, I would say Gmail blocks or locks the account if you send too many emails within couple of hours. Your account will be locked maximum for 24 hours.
If you have any questions or suggestions, please post a comment.