How to Send Bulk Emails using Gmail
Since the web interface of Gmail doesn’t support personalized emails, you should connect your Gmail account with Microsoft Outlook (via POP3 or IMAP) and also import the Gmail address book into your Outlook Contacts.
Now you can use the mail merge feature of Outlook to send personalized messages to every single Gmail contact from the desktop.
This may sound like an easy plan but there’re strict sending limits and, if you aren’t careful, Google may even block your Gmail account temporarily for up to 24 hours and you’ll neither be able to send nor receive any emails during that lock-out period.
Email Sending Limits in Google Apps
If you are using Gmail with Google Apps, you cannot send messages to more than 500 unique email addresses per day.
For instance, if you send one email to Person A and another one is addressed to Person B and C, you have already exhausted three slots (out of 500) even though only two messages left your Inbox.
Email Sending Limits for Gmail users
If you want to send bulk mails using a regular Gmail account, the rules are similar.
You can only send out emails to a maximum of 500 recipients during a 24 hour* period but if you are using a desktop client (like Outlook), that limit is reduced to 100 messages in a day.[*] The Gmail help site mentions this limit as 500 recipients per message but a Google employee on the Gmail support site has confirmed that this cap is not just per message but per day.
Workarounds for sending mass emails
With all these limitations in place, Gmail is obviously not the best option for reaching out to a very large customer base. However, if you have no other option, it may be a good idea to plan well in advance.
For Gmail: Distribute the mail merge process over 2-3 days so that you never exceed that 100 messages per day quota.
For Google Apps: You can either upgrade to a Premier edition or create multiple accounts in Google Apps as each will have its own 500-recipients limit.