Setting up email
Your portal may need to send emails to your end users (called Members). Those are all transaction emails like account email verification or password change confirmation. You can specify your own email server SMTP server details to deliver those emails from your organization email server or you can use 3rd party email delivery services like SendGrid.
How to decide what SMTP server to choose
Sending emails from your organization email server (could be local or cloud based) is supported and there is nothing wrong with it. However, you may want to consider if you want your organization server to be involved in transactional emails delivery. As it is best to talk to your IT provider or department before making this decision, the general rule is that email spam filters don't like repeatitive bulk emails, so in case your site will face lots of registrations you may prefer to use external service for those emails delivery. Low cost bulk email delivery providers (like SendGrid) can give you dedicated SMTP server connection, which you can use for Externable.
If you decide to use SendGrid, you need to register there and get your api key. Your SMTP connection details will look like this: SMTP Server: smtp.sendgrid.net SMTP Port: 587 SMTP Username: apikey SMTP password: your api key SMTP From Email: email that you set and authenticated in Externable
Setting SMTP details in Externable
Once you know your SMTP server details, go to your Externable subscription and instance you configure and set it like below: