block IP or spam or another problem

I setup an SMTP server(Postfix), Then I send an email to my gmail, I get the following email from gmail: This is the mail system at host mail.pahlevanzadeh.net. I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below. For further assistance, please send mail to postmaster. If you do so, please include this problem report. You can delete your own text from the attached returned message. The mail system : host gmail-smtp-in.l.google.com[142.250.31.27] said: 550-5.7.26 This message does not have authentication information or fails to 550-5.7.26 pass authentication checks. To best protect our users from spam, the 550-5.7.26 message has been blocked. Please visit 550-5.7.26 https://support.google.com/mail/answer/81126#authentication for more 550 5.7.26 information. m13si7030284qvk.215 - gsmtp (in reply to end of DATA command) Reporting-MTA: dns; mail.pahlevanzadeh.net X-Postfix-Queue-ID: 96B203C01C0 X-Postfix-Sender: rfc822; mohsen@pahlevanzadeh.net Arrival-Date: Sat, 6 Jun 2020 11:37:33 -0400 (AST) Final-Recipient: rfc822; m.pahlevanzadeh@gmail.com Original-Recipient: rfc822;m.pahlevanzadeh@gmail.com Action: failed Status: 5.7.26 Remote-MTA: dns; gmail-smtp-in.l.google.com Diagnostic-Code: smtp; 550-5.7.26 This message does not have authentication information or fails to 550-5.7.26 pass authentication checks. To best protect our users from spam, the 550-5.7.26 message has been blocked. Please visit 550-5.7.26 https://support.google.com/mail/answer/81126#authentication for more 550 5.7.26 information. m13si7030284qvk.215 - gsmtp salamkdsdjfi.eml Subject: salamkdsdjfi From: Mohsen Pahlevanzadeh Date: 6/6/20, 8:06 PM To: Pahlevanzadeh dwjkdjkdjvkdlvnfklvnfklvf Where's my problem?