Added an example .env file

.env.example

@@ -0,0 +1,21 @@
+
+# Mandatory: Server address of the SMTP server to use.
+#SMTP_SERVER=
+
+# Optional: (Default value: 587) Port address of the SMTP server to use.
+#SMTP_PORT=
+
+# Mandatory: Username to authenticate with.
+#SMTP_USERNAME=
+
+# Mandatory: Password of the SMTP user.
+#SMTP_PASSWORD=
+
+# Mandatory: Server hostname for the Postfix container. Emails will appear to come from the hostname's domain.
+#SERVER_HOSTNAME=
+
+# Optional: This will add a header for tracking messages upstream. Helpful for spam filters. Will appear as "RelayTag: ${SMTP_HEADER_TAG}" in the email headers.
+#SMTP_HEADER_TAG=
+
+# Optional: This will add a header for tracking messages upstream. Helpful for spam filters. Will appear as "RelayTag: ${SMTP_HEADER_TAG}" in the email headers.
+#SMTP_NETWORKS=