transport_maps and lookups reason

[Bokhan Artem]

Hello.

I have 'transport_maps = mysql:/etc/postfix/transport.cf' in 
configuration and want to understand the reason of every db lookup as I 
have some actions in mysql server based on queries count. Please explain 
them.

When sending single email these lookups are made:

1. "*"
2. "source@emal"
3. "destination@email"
4. "destination@email"

Especially what directives cause lookups over "mail from" address and 
why destination address is called twice?

I have single mysql inclusion in configuration.

postfix 3.3.0

Thanks.