Disable and enable mails in Joomla on the system level
Joomla Mail Configuration - Disable Sending Mails
In order to avoid sending mails at a moment when e.g. you are importing all your users into your user management application and it's just for migrating them to the new domain, you don't want to bother your customers with mails about this (it can be even a test with a site they are not supposed to see). Putting the 'Send Mail' option to 'No' wasn't enough as I experienced in a test run. So in order to avoid sending mails:
- Go to the System > Global Configuration Page
- Go to the tab "Server"
- Inside the mail settings (right lower part of the page)
- Put the Send Mail option to "No"
- Put your Mailer to SendMail
- Remove the path from the SendMail Path
Because there is no real valid means to send mails, your site will stop sending all mails. Of course, don't forget to restore your mail settings after you're done to avoid surprises afterwards ...
Joomla Default Mail Configuration
The default mail configuration for Joomla to send out mails is to use PHPMail and use a mailaddress from your own domain. Although there are recommendations on a couple of forums to use a mailaddress from your own domain, I tried also with a couple of gmail addresses and this worked fine for me. Up to you to decide what you will do.