diff --git a/.env.example b/.env.example
index a711c0a..cda261d 100644
--- a/.env.example
+++ b/.env.example
@@ -21,4 +21,7 @@
 #SMTP_NETWORKS=
 
 # Optional: Set this to a mounted file containing the password, to avoid passwords in env variables.
-#SMTP_PASSWORD_FILE=
\ No newline at end of file
+#SMTP_PASSWORD_FILE=
+
+# Optional: Set this to yes to always add missing From:, To:, Date: or Message-ID: headers.
+#ALWAYS_ADD_MISSING_HEADERS=yes
diff --git a/README.md b/README.md
index ef043b1..822dfdc 100644
--- a/README.md
+++ b/README.md
@@ -53,6 +53,7 @@ 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/
+* `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:`.
 
 To use this container from anywhere, the 25 port or the one specified by `SMTP_PORT` needs to be exposed to the docker host server:
 
diff --git a/run.sh b/run.sh
index 976cc66..4fd4cc9 100644
--- a/run.sh
+++ b/run.sh
@@ -36,6 +36,7 @@ add_config_value "smtp_use_tls" "yes"
 add_config_value "smtp_sasl_auth_enable" "yes"
 add_config_value "smtp_sasl_password_maps" "hash:/etc/postfix/sasl_passwd"
 add_config_value "smtp_sasl_security_options" "noanonymous"
+add_config_value "always_add_missing_headers" "${ALWAYS_ADD_MISSING_HEADERS:-no}"
 
 # Create sasl_passwd file with auth credentials
 if [ ! -f /etc/postfix/sasl_passwd ]; then