As u can see I have set 3 transport entry to use another postfix with sendgrid as relay. But I notice it will add 3 entry to mynetworks in main.cf.
If not mistaken you do not need to add the relay IP to mynetworks to work, right?
No problem actually. Just curious on the settings, that all.
If not mistaken, the transport IP do not need to be in the mynetworks to work.
The optional transport(5) table specifies a mapping from email addresses to message delivery transports and next-hop destinations. Message delivery transports such as local or smtp are defined in the master.cf file, and next-hop destinations are typically hosts or domain names. The table is searched by the trivial-rewrite(8) daemon.