Sending email using telnet command

Open your command prompt. Now, connect with telnet using the following command: telnet example.com 25 Type ehlo example.com. Some servers also accept helo in place of ehlo. ehlo example.com Type mail from: username@example.com: mail from: username@example.com Type rcpt to: friend@hotmail.com, friend2@yahoo.com (replace with your actual recipient name): rcpt to: user1@gmail.com, user2@gmail.com To write the message – type data, followed…

How to set mtu size for a network interface in redhat linux ?

1. To dynamically change the MTU in real time while the server is in use, ip link set dev eth0 mtu 1350 2. To make the change permanent, edit the interface configuration file (for instance eth0) vi /etc/sysconfig/network-scripts/ifcfg-eth0 AND ADD THE FOLLOWING LINE MTU=1350 3. To restart the Network Interface service network restart eth0

Validate SSL certificate using OpenSSL command

Check a Certificate Signing Request (CSR) $openssl req -text -noout -verify -in CSR.csr Check a private key $openssl rsa -in privateKey.key -check Check a certificate $openssl x509 -in certificate.crt -text -noout Check a PKCS#12 file (.pfx or .p12) $openssl pkcs12 -info -in keyStore.p12