There is a CWP server vulnerability. Please help me.

Mail is being sent from my domain name against my request on my CWP server.HELP

Please help URGENTLY.
Log records as follows:
helo=87-207-170-128.dynamic.chello.pl, from=qdzftt632@xxx.com.tr, to=qdzftt632@xxx.com.tr,

The domain mentioned here is mine, but I do not have such mails. Spam is constantly being sent.

_dmarc   14400   IN   TXT   "v=DMARC1; p=reject"
@   14400   IN   TXT   "v=spf1 +a +mx +ip4:xxxxxxx ip4:xxxxxxx -all"

also it is not possible for them to steal any password from me.

Well, yes there was a vulnerability. But if you have updated to 0.9.8.1148 or newer (we are 2 updates past the vulnerable version), you should be safe. But it sounds as if your Postfix installation is not sufficiently hardened, and perhaps CSF/LDF is not doing all it can do for you. Also, consider installing Mod_Security with the Comodo ruleset.