550 5.7.64 TenantAttribution; Relay Access Denied [No TLS]

 Troubleshooting:

1) create/enable 'Connector' in 'Exchange'

Show all > Exchange > EAC (Exchange Administrative Control) > Mail flow > Connectors

2) check into created connector if enabled an option like 'keep Exchange headers'

Linux Rsync with particular extension

 rsync -zarv --prune-empty-dirs --include "*/"  --include="*.gif" --exclude="*" ./ ../gifs/