Every credential field a connection has can also be set from wp-config.php or your server’s
environment instead of the database. A defined, non-empty constant always overrides the value stored
for that field.
The naming rule
BOOLEANSMTP_{DRIVER}_{KEY}— the connection’s driver, then the field’s key, both upper case.
Example: Custom SMTP
A Custom SMTP connection’s SMTP Username and Password fields are username and password, so
setting these in wp-config.php overrides them for every Custom SMTP connection on the site:
define('BOOLEANSMTP_SMTP_USERNAME', 'your-smtp-username');
define('BOOLEANSMTP_SMTP_PASSWORD', 'your-smtp-password');On the connection form, choose Credential Storage: WP Config to read the constant from
wp-config.php, or Environment to read it as an OS environment variable instead — either way, leave
the field itself blank.
Use a non-empty value. An empty constant or environment value does not replace a credential stored in the database; if there is no stored credential, the connection still needs one.
See the full list of constants for every driver’s field names and the constants BooleanSMTP reads outside connection settings.