feat: Add support to load username from file

README.md

@@ -66,6 +66,11 @@ The following env variable(s) are optional.
 * `SMTP_PASSWORD_FILE` Setting this to a mounted file containing the password, to avoid passwords in env variables. Used like
     -e SMTP_PASSWORD_FILE=/secrets/smtp_password
     -v $(pwd)/secrets/:/secrets/
+
+* `SMTP_USERNAME_FILE` Setting this to a mounted file containing the username, to avoid usernames in env variables. Used like
+    -e SMTP_USERNAME_FILE=/secrets/smtp_username
+    -v $(pwd)/secrets/:/secrets/
+
 * `ALWAYS_ADD_MISSING_HEADERS` This is related to the [always\_add\_missing\_headers](http://www.postfix.org/postconf.5.html#always_add_missing_headers) Postfix option (default: `no`). If set to `yes`, Postfix will always add missing headers among `From:`, `To:`, `Date:` or `Message-ID:`.
 
 * `OVERWRITE_FROM` This will rewrite the from address overwriting it with the specified address for all email being relayed. Example settings:

run.sh

@@ -13,8 +13,9 @@ function add_config_value() {
  postconf -e "${key} = ${value}"
 }
 
-# Read password from file to avoid unsecure env variables
+# Read password and username from file to avoid unsecure env variables
 if [ -n "${SMTP_PASSWORD_FILE}" ]; then [ -f "${SMTP_PASSWORD_FILE}" ] && read SMTP_PASSWORD < ${SMTP_PASSWORD_FILE} || echo "SMTP_PASSWORD_FILE defined, but file not existing, skipping."; fi
+if [ -n "${SMTP_USERNAME_FILE}" ]; then [ -f "${SMTP_USERNAME_FILE}" ] && read SMTP_USERNAME < ${SMTP_USERNAME_FILE} || echo "SMTP_USERNAME_FILE defined, but file not existing, skipping."; fi
 
 [ -z "${SMTP_SERVER}" ] && echo "SMTP_SERVER is not set" && exit 1
 [ -z "${SERVER_HOSTNAME}" ] && echo "SERVER_HOSTNAME is not set" && exit 1