Normally, to check if my server smtp connection alive, I just do telnet to port 25 from my workstation. if the smtp banner displayed, it means that the connection to the smtp server is good. I have done this for years. 
1 | $ telnet smtp.example.com 25 |
2 | Trying xxx.xxx.xx.xxx... |
3 | Connected to xxx.xxx.xx.x. |
4 | Escape character is '^]'. |
5 | 220 smtp.example.com ESMTP Postfix |
14 | 250-ENHANCEDSTATUSCODES |
19 | Connection closed by foreign host. |
Although many tools that are deliberately created for this purpose, still, I prefer just using telnet to port 25. I have made a simple perl script, with the intention that the things I do for years manually can be done automatically.
Modules required:
