Logging into your email account to retrieve email seems fairly simple. However, there is technology working behind the scenes, such as simple mail transfer protocol (SMTP) and internet networks to ensure you can send and receive email. Think about SMTP as a mail carrier, sorting and delivering messages to mail servers. These messages are then delivered directly to your email inbox.

SMPT is responsible for transmitting email across Internet networks (IPs). This technology is used specifically for sending outgoing email. Clients typically use applications such as Internet Message Access Protocol (IMAP) or Post Office Protocol (POP) to access to their email box. For example, if you send an email it goes to a mail server using SMTP. The mail client will then deliver it to the user’s mailbox.

SMTP is responsible for a little more then just deliver messages to servers. It performs several functions that streamlines the delivery process.

-It evaluates the configuration and grants permission to the computer who is trying to send a message.
-It can also track if the message was sent successfully. If it isn’t, an error message is sent to the sender.
-Extended SMTP is a little more advanced then older versions. It helps cut back on email spam.

Previous versions of this technology had limiting figures, such as the location of the client within the network. SMTP allows clients to submit emails quickly regardless of the recipients location. Thats because current SMTP technology uses a clients authentication (which are their accreditations) instead of the license IP address to send email.

Both are protocol.

465 is for SMTPS protocol, In this SSL encryption is started automatically before any SMTP level communication.

587 is for MSA protocol. SSL encryption may be started by STARTTLS command at SMTP level(if server supports). In this ISP does not filter server’s EHLO reply.It helps to stop outgoing spam email.

telnet {smtp_domain_name} {smtp_port}