feat: Allow disabling SMTPUTF8

.env.example

@@ -34,3 +34,6 @@
 
 # Optional: This will output the subject line of messages in the log.
 #LOG_SUBJECT=yes
+
+# Optional: This will disable (no) or enable (yes) the use of SMTPUTF8
+#SMTPUTF8_ENABLE=no

README.md

@@ -81,6 +81,8 @@ The following env variable(s) are optional.
 
 * `LOG_SUBJECT` This will output the subject line of messages in the log.
 
+* `SMTPUTF8_ENABLE` This will enable (default) or disable support for SMTPUTF8. Valid values are `no` to disable and `yes` to enable. Not setting this variable will use the postfix default, which is `yes`.
+
 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:
 
     docker run -d --name postfix -p "25:25"  \

run.sh

@@ -86,6 +86,12 @@ if [ ! -z "${SMTP_NETWORKS}" ]; then
 fi
 add_config_value "mynetworks" "${nets}"
 
+# Set SMTPUTF8
+if [ ! -z "${SMTPUTF8_ENABLE}" ]; then
+  postconf -e "smtputf8_enable = ${SMTPUTF8_ENABLE}"
+  echo "Setting configuration option smtputf8_enable with value: ${SMTPUTF8_ENABLE}"
+fi
+
 if [ ! -z "${OVERWRITE_FROM}" ]; then
   echo -e "/^From:.*$/ REPLACE From: $OVERWRITE_FROM" > /etc/postfix/smtp_header_checks
   postmap /etc/postfix/smtp_header_checks