Question

What are the limitations of Gmail's SMTP? How many emails can it send per second/minute/hour?

Answer 1

Google Gmail Email Send Rate Limit & Restrictions

The following restrictions apply when sending emails from a Google Gmail account:

Gmail email send limit - no more than 500 recipients per message for the Gmail web interface, or max 100 recipients if you are using an email client software.

Gmail other SMTP limits - outgoing messages sent via Google Gmail can not exceed 10Mb per email (including attachments)

Google Mail Policy - http://www.google.com/mail/help/program%5Fpolicies.html

Google Mail SMTP restriction expiry method - the restriction is automatically removed within 24 hours after the limit was reached.

Answer 2

The from field is always the account name which authenticated to smtp. If you're using this for something other than person mail you may want to consider creating account specific to the purpose you have in mind.

Answer 3

Apart from the limitations:

The Gmail SMTP server automatically moves a copy to your Sent Items. (So, when using that server, be sure to set up your email client to use only that server. If you don't, then when your client falls back to some other server, you won't have a copy in your Sent Items.)

If you want to use another Sender address, then see Adding a custom 'From' address; if you don't then Gmail will change it into your gmail.com address. For fine tuning see the recent new feature Send mail from another address without "on behalf of".