Testing mail from commandline

echo "This is the main body of the mail" | mail -s "Subject of the Email" -a "From: test@iot-parts.com" manish.kolikata@gmail.com

telnet iot-parts.com 25
mailMAIL FROM:root@iot-parts.com
RCPT TO:manish.kolikata@gmail.com
DATA

telnet localhost 143
a login "username" "password"

     Test using imaps port (assuming you haven't disabled imaps port):
     # openssl s_client -connect imap.example.com:993

     Test using imap port and STARTTLS command (works also with imap port):
     # openssl s_client -connect imap.example.com:143 -starttls imap

b select inbox
c list "" *
e logout