How to Keep an Eye on an SMTP Server


A lot happens behind the scenes when a user in an organization writes an email. When the user presses the send button, the message is sent to a service that uses the basic mail transport protocol (SMTP). The SMTP service is responsible for contacting the recipient mail server and transferring the message to the mail server. Mail cannot be sent if the SMTP service stops responding. The best way to Buy SMTP Service from NitroMail.io.

A mail server’s ability to transmit email can be lost for various reasons. Here are a few examples:

1. The mail server’s Internet connection may be lost.

2. The mail server may run out of resources (such as disc space), causing the operating system to crash or hang.

3. A mail administrator could make a setup mistake that confuses the service about how to send emails.

4. A mail server may be added to a blocklist, preventing it from delivering mail to any receiving server that uses it as a resource to reduce spam.

Because outgoing mail is a crucial function for almost every organization, it is critical to have some way in place to monitor the service. Some website monitoring services additionally enable SMTP monitoring. This is how it works:

First, the website monitoring service will attempt to connect to the SMTP server using a socket connection via the transmission control protocol (TCP). This entails sending an SYN packet to the SMTP server and waiting for an ACK message. If no acknowledgment is received, the monitoring service understands that the SMTP service is not responding to requests.

Following that, if the ACK was received and a socket connection was properly established, the monitoring service will attempt to interact via protocol commands. Here’s one possibility (which you can test for yourself using the well-known terminal application Telnet):

1. If the connection is successful, the mail server will display a banner like “Connected to mail.somedomain.net.” Something is most likely incorrect if no flag is sent.

2. The monitoring service will then present itself as a mail user by issuing the “HELO” command followed by the email’s origin domain. So the total power might be “HELO my.domain.net.”

3. If everything is in order, the SMTP server will respond, “250 Hello my.domain.net, pleased to meet you.”

It is then determined that the SMTP server is responding to connection requests and is ready to receive additional commands. If the monitoring service detects a failure at any of these places, it can report the failure, the time, and any content received, which may aid in diagnosing the problem. The program will then deliver notifications through email, SMS, or even phone calls.

For most monitoring systems, this is sufficient to provide a rudimentary sanity check on the mail server’s operation. Some website monitoring services go even further, allowing you to create a script to verify the mail-sending process extensively. This more complex approach also requires interaction with a POP3 or IMAP4 mail server.

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