feat: docs: add instructions to setup local SMTP server

docs/HACKING.md

@@ -7,7 +7,8 @@
 3. Virtualenv
 4. GNU make
 5. PostgreSQL
-6. (Optionally) Docker: used to spin up PostgreSQL instance
+6. SMTP server(instructions available for Docker setup)
+7. (Optionally) Docker: used to spin up PostgreSQL instance
 
 ## Setup
 
@@ -57,6 +58,24 @@ instance_
  docker start $db
 ```
 
+4. Setup SMTP server
+
+We are using the excellent development SMTP server
+[maildev](https://maildev.github.io/maildev/).
+
+```bash
+docker create --name hostea-smtp \
+	-p 1080:1080 \
+	-p 10025:1025  \
+	maildev/maildev \
+	--incoming-user \
+	admin \
+	--incoming-pass password && \
+docker start hostea-smtp
+```
+
+SMTP is available at port 10025 and the email web interface at port 1080
+
 4. Install Dependencies
 
 ```bash