WordPress
WordPress and Email
For basic functionality (new user, lost password, comment moderation) your WordPress instance needs to be able to send email.
Google Apps
You can setup WordPress to handle your email through Google Apps (GSuite) with the gmail-smtp plugin. This works whether you have a single GMail address, or the full GSuite for your domain. One nice advantage of using this method is that DKIM is handled by Google automatically.
MailGun
MailGun is a better delivery service provider in our experience. If you want a fuller feature set for tracking your mail campaigns and so-forth, then MailGun could be the right sender for your needs.
CiviCRM
If you integrate CiviCRM into your WordPress installation, then you might also have configured CiviCRM independently to hand off email to MailGun or another provider through the SMTP configuration. Using MailGun is preferred (over plain 'mail()' or even GSuite) when your WordPress website is being used to send monthly messages (even just a few thousand) to your newsletter and other list subscribers.
CLI
WordPress has a command line interface that lets you administer the system; even remotely. See also CiviCRM/WordPress
For example, you can quickly get a list of your users, with ID, login, display_name, user_email, user_registered and roles
sudo -u www-data wp user list
The cli integrates with CiviCRM -- and even allows you to INSTALL CiviCRM into your WordPress site, not just manage it. For details: see CiviCRM/WordPress
