According to the Phabricator documentation:
Phabricator supports the following configuration sources, from highest priority to lowest priority:
Database: Values are stored in the database and edited from the web UI by administrators. They have the highest priority and override other settings.
Local: Values are stored in conf/local/config.json and edited by running bin/config.
Config Files: Values are stored in a config file in conf/. The file to use is selected by writing to conf/local/ENVIRONMENT, or setting the PHABRICATOR_ENV configuration variable. See below for more information.
Defaults: Defaults hard-coded in the Phabricator source, which can not be edited. They have the lowest priority, and all other settings override them.
So, you can change the value of the email properties through the Phabricator application ("Config -> PHPMailer" menu) or by running the command:
/opt/bitnami/apps/phabricator/htdocs/bin/config set property value
You can take a look at the configuring outbound email Phabricator documentation to find the exact properties you need to configure:
Also, we have a guide that may help you configuring Amazon SES: