These changes cause narrowing of the lumbar spinal canal which is known as spinal stenosis. Spinal stenosis is like the lime build-up on the inside of a garden hose. Over time, it narrows the diameter of the hose, just as spinal stenosis narrows the spinal canal.
SMTP Protocol: The SMTP (Simple Mail Transfer Protocol) protocol is used by the Mail Transfer Agent (MTA) to deliver your eMail to the recipient's mail server. The SMTP protocol can only be used to send emails, not to receive them.
Whenever a message is sent from the client, the kernel of the client automatically puts its port number and its IP address of the interface inside the packet, and sends it out. This packet on reaching the server will go through the protocol stack from bottom to top, i.e link, network, transport layer, application layer.