Improve SMTP settings

.env.sample

@@ -46,6 +46,8 @@ SECRET_DB_PASSWORD_VERSION=v1
 #COMPOSE_FILE="$COMPOSE_FILE:compose.smtp.yml"
 #SMTP_HOST="mail.example.com"
 #MAIL_FROM="wordpress@example.com"
+#SMTP_USER="wordpress@example.com"  # optional, defaults to MAIL_FROM
+#SMTP_OVERRIDE_FROM=on  # force "From" to MAIL_FROM, usually necessary
 #SMTP_PORT=587
 #SMTP_AUTH=on
 #SMTP_TLS=on