Sending Spam

Hi i found out in logs that i am sending spam (from server) cannot locate which website user is doing it or is the server. I canot receive email may be due to the cue. How can i proceed, i have not aclue how to stop it or how to clear the cue is sending to yahoo or even stopping this form happening again.

This is part of the log:

Apr 1 08:47:30 fra postfix/smtp[30163]: 300F4F50B7C7: lost connection with mta6.am0.yahoodns.net[67.195.228.110] while sending RCPT TO
Apr 1 08:47:30 fra postfix/smtp[30194]: 33FC1F48A611: host mta6.am0.yahoodns.net[67.195.228.94] said: 421 4.7.0 [TSS04] Messages from 209.182.238.205 temporarily deferred due to user complaints - 4.16.55.1; see Help for Yahoo Postmaster (in reply to MAIL FROM command)
Apr 1 08:47:30 fra postfix/smtp[30194]: 33FC1F48A611: lost connection with mta6.am0.yahoodns.net[67.195.228.94] while sending RCPT TO
Apr 1 08:47:30 fra postfix/smtp[30169]: 39882F48B9D8: host mta5.am0.yahoodns.net[67.195.204.72] said: 421 4.7.0 [TSS04] Messages from 209.182.238.205 temporarily deferred due to user complaints - 4.16.55.1; see Help for Yahoo Postmaster (in reply to MAIL FROM command)
Apr 1 08:47:30 fra postfix/smtp[30169]: 39882F48B9D8: lost connection with mta5.am0.yahoodns.net[67.195.204.72] while sending RCPT TO
Apr 1 08:47:30 fra postfix/smtp[30162]: 3E630F50A491: host mta7.am0.yahoodns.net[67.195.204.73] said: 421 4.7.0 [TSS04] Messages from 209.182.238.205 temporarily deferred due to user complaints - 4.16.55.1; see Help for Yahoo Postmaster (in reply to MAIL FROM command)
Apr 1 08:47:30 fra postfix/smtp[30162]: 3E630F50A491: lost connection with mta7.am0.yahoodns.net[67.195.204.73] while sending RCPT TO

You have to do some changes in postfix config and I would also recommend restricting -
Only allowed users can use SMTP
disable PHP mail function for all php. Only SMTP can send emails from the application.

I am 100% sure this will fix your issue.