There are 2 main methods for sending/testing outgoing mail: * __Telnet/nc__ * __swaks__ \\ \\ My favourite is using swaks as its easy to use and quick. You will probably need to install though: \\ ==== SWAKS ==== Swaks can be found in the epel repository. Make sure you have this repo enabled and then run: # yum install swaks -y \\ === Testing your local mail server === The following command tests your local mail configuration (postfix). This includes the relay that may be configured with it. swaks --to random_email@gmail.com --server 127.0.0.1 -from luke@example.com \\ === Testing the relay host === The following command will send mail directly to the relay (for example sendgrid or mailgun). \\ Change "username" to the username you normally authenticate with to the relay host and you will be prompted for a password once you run the following command: swaks --to random_email@gmail.com --server smtp.sendgrid.net:587 --auth-user username -tls \\ \\ ==== Telnet ==== Command: telnet localhost 25 Response: Trying ::1... Connected to localhost. Escape character is '^]'. 220 cloud-server-03.localdomain ESMTP Postfix \\ Command HELO localhost Response: 250 cloud-server-03.localdomain \\ Command mail from: luke@localdomain.com Response: 250 2.1.0 Ok \\ Command rcpt to: luke@lukeslinux.co.uk Response: 250 2.1.5 Ok data 354 End data with . Type some data and then end the email with a `.` on a line by itself. \\ Press enter to escape and the type quit