Which menu do I need to check SMPT settings ?

I am going to use Swift Mailer library for sending my emails.

In the docs it says:

Many SMTP servers have limits on the number of messages that may be sent during any single SMTP connection.

and

If your SMTP server has restrictions in place to limit the rate at which you send emails, then your code will need to be aware of this rate-limiting.

So I would like to see what my restrictions are set at.

Where can I find them ?

Thanks

in the postfix module under delivery rates (if you are using postfix)