Postfix SMTP Recipient address rejected: User unknown in virtual mailbox table

Hi to all!
I've some problems with the Postfix SMTP server.

I've disabled amavis and clamav following this steps: https://www.faqforge.com/linux/cont...ilter-and-antivirus-functions-in-ispconfig-3/ but it's not the problem.

The server is: server2.opt-media.es

The problem: SMTP Error (550): Failed to add recipient "[email protected]" (5.1.1 <[email protected]>: Recipient address rejected: User unknown in virtual mailbox table).

I receive this error only when trying to send email to an external recipient @otherdomain.com but not all. I mean: The server is server2.opt-media.es and the MX record is even server2.opt-media.es. Wordpress contact forms are ables to send email either to local domain, to gmail but NOT to opt-media.net (and don't know how many others).
Other rare problem, server is able to send emails from Wordpress, but not from Roundcube to the same recipient addresses. Like wordpress can send to [email protected] but the same address can't send outbound emails to himself, or to @gmail.com or to someone. No errors logged this time.

MAYBE THIS CAN HELP? Think not cause my primary MX it's working: https://www.howtoforge.com/postfix_backup_mx

I'm going crazy with that, it was working properly and perfectly. Now i encounter that error.

 

If you see this on your server, it means [email protected] has neither mailbox, alias or forward address. In other words, that recipient does not exist on this server.
On the other hand, MX record for opt-media.net points to Google servers:

Code:

$ host opt-media.net
opt-media.net has address 213.180.70.147
opt-media.net mail is handled by 30 ASPMX2.GOOGLEMAIL.COM.
opt-media.net mail is handled by 30 ASPMX5.GOOGLEMAIL.COM.
opt-media.net mail is handled by 30 ASPMX4.GOOGLEMAIL.COM.
opt-media.net mail is handled by 20 ALT1.ASPMX.L.GOOGLE.COM.
opt-media.net mail is handled by 20 ALT2.ASPMX.L.GOOGLE.COM.
opt-media.net mail is handled by 10 ASPMX.L.GOOGLE.COM.
opt-media.net mail is handled by 30 ASPMX3.GOOGLEMAIL.COM.
tale@myhost /home/taleman

So mails [email protected] should not be arriving at your server, they should go to Google GMail.
Is there a reason to disable amavis and clamav?