Your mailing application can't function without proper mail settings configured. There are two options for sending mail:
Default sending method (sendmail, qmail, etc)
SMTP
The "Default sending method" will send email using PHP's mail() function, which uses the default MTA on your server. MTA stands for "Mail Transport Agent." Examples of MTAs include Sendmail, Qmail, PowerMTA, etc.
The SMTP option will allow you to send emails from an external server, by entering your SMTP host name, user name, password, and port.
Though many users will be fine using our software's default mail sending method, which uses PHP's mail() function, you may find that the default mail() function is limited or disabled on your server, and as such, you may decide to send emails from an external SMTP server instead. Furthermore, many of our clients wish to send emails from multiple servers, or change the speed at which our software sends email.
These options can be changed on the Settings page in our software. On the Settings page, scroll down to the Mail Sending section. There, you will see that the default mail sending settings is set to PHP's mail() function.
Click Edit next to the Default if you wish to change the speed at which emails are sent (throttling settings), or if you wish to change the method from mail() to SMTP. You can also click "Add New Mail Sending Connection" if you wish to add multiple SMTP accounts to send with (the software will rotate sending between all accounts you add). If you'd like to add an SMTP account, choose the "SMTP" option, and you will see the option to add your SMTP connection details like so:
Sending Speed
When adding mail connections, you'll notice additional configuration options:
Each of these options allows you to further control your mail configuration.
Emails Per Cycle: Specify a number here if you have more than one mail settings connection. You can have the application send a certain number of emails from one connection, then move on to the next connection.
Enable sending throttling and pausing: Check this option if you wish to reduce your mail servers' load by forcing a pause after a specific number of emails are sent.
Limit number of emails to send for a specific time period: Check this option if you'd like to limit the number of emails sent in a given time period (hour or day).
Used by User Groups: This powerful control lets you specify which mail sending options are used for each user group. If you set up your mailing application for different clients, for example, you may want separate SMTP settings for each client (group). See, also, the article on User Groups.
The following article discusses in detail how to add multiple SMTP accounts, and how to configure throttling settings to meet your needs: Mail Sending Throttling Settings Explained
