What the .....? What's this? Weird lines in my mail log...

Sometimes I see some weird lines in my mail log.
Who sees lines like these too? It's just weird... It's a jungle out there.

Code:

Jan 20 15:58:51 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /system_api.php HTTP/1.1
Jan 20 15:58:55 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /c/version.js HTTP/1.1
Jan 20 15:58:59 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /streaming/clients_live.php HTTP/1.1
Jan 20 15:59:02 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /stalker_portal/c/version.js HTTP/1.1
Jan 20 15:59:06 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /client_area/ HTTP/1.1
Jan 20 15:59:10 vps2 postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]: GET /stalker_portal/c/ HTTP/1.1

Jan 22 15:02:02 s2 postfix/smtpd[10857]: warning: hostname 14-scan-andrew.foma-gmail.com does not resolve to address 188.166.157.194: Name or service not known
Jan 22 17:36:02 s2 postfix/smtpd[17823]: warning: hostname 23-scan-andrew.foma-gmail.com does not resolve to address 143.110.158.81: Name or service not known
Jan 22 18:27:39 s2 postfix/smtpd[20384]: warning: hostname 46-scan-andrew.foma-gmail.com does not resolve to address 138.197.158.236: Name or service not known

 

Code:

postfix/submission/smtpd[27907]: warning: non-SMTP command from unknown[159.89.171.117]

Someone from India is trying to access your host but in a wrong way. Using Internet Search Engines with error message often explains what it means.

Code:

warning: hostname 14-scan-andrew.foma-gmail.com does not resolve to address 188.166.157.194:

Incorrectly configured e-mail server tries to send to your server.