Mail Protocol: SMTP
SMTP refers to using another server (not your hosting) to deliver your emails.
SMTP Host: type the IP address or the name of the server
SMTP Username: here you have to type the full email address of the email account you created earlier. Don't type just the username part, but the whole address (e.g. firstname.lastname@example.org)
SMTP Password: type the password of the same email account. Make sure your mail password contains only UTF-8 characters.
SMTP Port: Port may vary. The most common ports are 25, 465, 587
SMTP Timeout: Default value 5. Sometimes you need to increase this value to give more time for the mailer to answer.
Example of Gmail SMTP
Mail Protocol – SMTP
SMTP Host - ssl://smtp.gmail.com
SMTP Username - your username (aka username if your email is email@example.com)
SMTP Password - your Gmail password
SMTP Port - 465
As a security precaution, Google (gmail) may prevent an application from accessing your account if it's the first time Google has seen this application sign in to your account, or if it's attempting to sign in from a new location.
Gmail send email “Suspicious sign in prevented” and after login in Gmail ask you to confirm this attempt as legal. Just follow Google instructions. Also please check if you have any firewall on your server that blocks outgoing connections.