First, you must install the plugin from the WordPress plugin installer, which if we search for Postman SMTP, it will be the first one that appears

Then click on the install now button that appears on the plugin

and once installed, the activate button will appear, click on activate to activate it and now the plugin configuration options will appear in the menu, under Settings click on Postman SMTP and the following window will appear

Where we see 2 options in the configuration

Start the wizard

show all setting

if we click on the blue Start the wizard button, the configuration manager will start

where it tells us that if we have the configuration of another plugin for sending mail, this plugin can copy the configuration, in our case we are going to give none to configure it ourselves, and click on Next

In this first step, it will ask us for the email from which the shipments will be made and the name of the sender, once filled in, we mark Next

In this step, it asks us for the name of the server, localhost refers to the server where it is hosted

it would be more correct to put the name of the domain or mail.domain.com

several examples:

google.com --> mail.google.com

google.es --> mail.google.es

wikipedia.org --> mail.wikipedia.org

in this step we are going to select SMTP with port 587 and click on Next

In this step, we are going to fill in the email and password, once the fields are completed, click on Next

And the plugin configuration ends

Now we can click on Finish to save the configuration and it will take us to the home page (where we chose Start the wizard)

once on this page we look for

and click on this option

The following window opens where we can put an email account to start a test, then click on Next

Where it informs us of the status of the message. And, if everything is correct, the message will be sent correctly to the destination