Mail delivery failed: returning message to sender

[alemmsm]

Hello
I can not send or receive emails from roundcube
I think this happened after updating the email programs...

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

......@gmail.com
host gmail-smtp-in.l.google.com [142.251.5.27]
SMTP error from remote mail server after end of data:
550-5.7.1 [144.91.... 12] Our system has detected that this message is
550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail,
550-5.7.1 this message has been blocked. Please visit
550-5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError
550 5.7.1 for more information. r185-20020a1c44c2000000b003944023ed54si21085979wma.10 - gsmtp
Reporting-MTA: dns; server.majorproductive.ir

Action: failed
Final-Recipient: rfc822;....@gmail.com
Status: 5.0.0
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 [144.91...... 12] Our system has detected that this message is
550-5.7.1 likely unsolicited mail. To reduce the amount of spam sent to Gmail,
550-5.7.1 this message has been blocked. Please visit
550-5.7.1 https://support.google.com/mail/?p=UnsolicitedMessageError
550 5.7.1 for more information. r185-20020a1c44c2000000b003944023ed54si21085979wma.10 - gsmtp

 

[Daniel-Doggy]

Your email is blocked by gmail as it is marked as potential spam.

For more info see: https://support.google.com/mail/?p=UnsolicitedMessageError

 

[Ohm J]

Check your IP at https://check.spamhaus.org

 

[Richard G]

Even better, check here, this checks multiple spam lists.

Email Blacklist Check - IP Blacklist Check - See if your server is blacklisted

mxtoolbox.com

However, the ip is not blacklisted, so the reason is like @realcryptonight stated, mail is marked as potential spam.
Normally it's probably the content, in your case it's most certainly DNS records.

server.majorproductive.ir -> there are no nameservers pointing to this hostname.

Your DNS records are not correct, 2 different ip's are pointing to the same server on an nslookup, so duplicate A records for the same name":

[root@server23: ~]# nslookup server.majorproductive.ir
Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   server.majorproductive.ir
Address: 104.21.11.156
Name:   server.majorproductive.ir
Address: 172.67.166.98
Name:   server.majorproductive.ir
Address: 2606:4700:3031::ac43:a662
Name:   server.majorproductive.ir
Address: 2606:4700:3031::6815:b9c

A reverse lookup from both the ipv4 points to nothing.

For Gmail to work, you need correct DNS records to begin with, so just 1 ipv4 pointing to the hostname not 2 different ones, and you also need a rDNS/PTR record, which points to hostname. Both are not present so Gmail will refuse mail.
Same goes for the ipv6 addresses.