554 5.7.1 Relay access denied [closed]

@Jaan Postfix will accept the mail only if the email address falls under anyone of the following address classes.

  • Local domain Class
  • virtual Alias Class
  • Virtual mailbox class
  • Relay class

Or if the connecting host is listed under mynetworks (default class). More about postfix address classes here

Your screenshots show that you are setting up your domain xxx as local domain class. i have never used any GUI for postfix administration. Ensure the following configurations exist in main.cf

mydestination = xxx
# to consider xxx domain as local address class
# add localhost localhost.$mydomain also to mydestination after your testing
# valid users under mydestination domains should be specified using local_recipient_maps

#local_recipient_maps = proxy:unix:passwd.byname $alias_maps
# commented it out, because default setting is proxy:unix:passwd.byname $alias_maps
# Now all your UNIX users and special aliases in $alias_maps can receive mails