How to test mail server in linux

There are several ways to test a mail server in Linux:

Using the telnet command:
```
telnet localhost 25
```
This will establish a connection to the mail server on port 25 (the default SMTP port). You can then type commands like HELO or EHLO to test the server's response.
Using the nc command:
```
nc localhost 25
```
This is similar to using telnet, but nc is a more powerful tool that allows you to send and receive data.
Using a mail client:
```
mutt -s "Test email" [email protected]
```
This will send a test email to the specified recipient using the mutt mail client.
Using the msmtp command:
```
msmtp -v -a [email protected]
```
This will send a test email to the specified recipient using the msmtp command-line mail client.
Using the postfix command:
```
postfix -v -c /etc/postfix/main.cf -o mydestination=localhost
```
This will start the Postfix mail server in debug mode and allow you to test its functionality.
Using a mail testing tool:
```
swaks -s localhost -f [email protected] -t [email protected]
```
This will send a test email to the specified recipient using the swaks mail testing tool.
Using the mail command:
```
mail -s "Test email" [email protected]
```
This will send a test email to the specified recipient using the mail command-line mail client.
Using the sendmail command:
```
sendmail -v -t < /dev/null
```
This will send a test email to the specified recipient using the sendmail command-line mail client.
Using the mailx command:
```
mailx -s "Test email" [email protected]
```
This will send a test email to the specified recipient using the mailx command-line mail client.
Using a mail server testing tool:
```
mail-tester.com
```
This is a web-based tool that allows you to test your mail server's functionality and receive feedback on its performance.

Remember to replace localhost and [email protected] with the actual hostname and email address of your mail server and recipient.

Mail Knowledge

How to test mail server in linux