Postfix Relay Loops Back To Myself

Question

I have 2 servers, let me illustration like this:

Server A = Exchange Server (mail.fendyfy.com)
Server B = SMTP Server (Postfix) on VPS (smtp.fendyfy.com)

I want my server A to fully Send&Receive emails from server B (because server A port 25 is blocked by ISP)
Now I already can Send external emails using smarthost and configuring the port to 587
But I can't receive external emails, the email status is Bounced. Is there something wrong with my configuration?

There are the error logs when I try sending from Gmail:

smtp postfix/relay/smtp[13454]: A303C201AA: to=<administrator@fendyfy.com>, relay=none, delay=0.47, delays=0.45/0.01/0.01/0, dsn=5.4.6, status=bounced 

(mail for fendyfy.com loops back to myself)

This is my Postfix configuration:

smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination<br>
myhostname = mail.fendyfy.com<br>
mydomain = fendyfy.com<br>
myorigin = $mydomain<br>
mydestination =<br>
local_recipient_maps =<br>
relayhost =<br>
mynetworks = 0.0.0.0/0<br>
relay_domains = fendyfy.com<br>
mailbox_command = procmail -a "$EXTENSION"<br>
mailbox_size_limit = 0<br>
recipient_delimiter = +<br>
inet_interfaces = all<br>
inet_protocols = all

Answer 1

Have you added the relay server IP to the receive connector in exchange server? If not, follow these guidance：Receive connectors and How to Configure a Relay Connector for Exchange Server 2010

In addition, a similar thread for your reference as well.

Sorry for that I'm not familiar with Postfix, but i have done some research, here are some solutions in the blog for your reference: Postfix mail for domain.com loops back to myself Error and Solution