[Docs] Add documentation for SMTP settings (#279)

docs/development/environment-setup/mac-os.md

@@ -104,9 +104,6 @@ launchctl unload ~/Library/LaunchAgents/homebrew.mxcl.redis.plist
 brew install imagemagick
 ```
 
-Next: [Read project setup to install project dependencies](https://www.chatwoot.com/docs/dependencies) 
-
-
 ### Install Docker
 
 This is an optional step. Those who are doing development can install docker from [Docker Desktop](https://www.docker.com/products/docker-desktop).

docs/development/environment-setup/ubuntu.md

@@ -106,5 +106,3 @@ sudo systemctl enable redis-server.service
 ```bash
 sudo apt-get install imagemagick
 ```
-
-Next: [Read project setup to install project dependencies](https://www.chatwoot.com/docs/dependencies) 

docs/development/environment-setup/windows.md

@@ -100,5 +100,3 @@ sudo systemctl enable redis-server.service
 ```bash
 sudo apt-get install imagemagick
 ```
-
-Next: [Read project setup to install project dependencies](https://www.chatwoot.com/docs/dependencies)

docs/development/project-setup/environment-variables.md

@@ -32,6 +32,14 @@ FB_APP_ID=
 
 For development, you don't need an email provider. Chatwoot uses [letter-opener](https://github.com/ryanb/letter_opener) gem to test emails locally
 
+For production use, use the following variables to set SMTP server.
+
+```bash
+SMTP_ADDRESS=
+SMTP_USERNAME=
+SMTP_PASSWORD=
+```
+
 ### Configure frontend URL
 
 Provide the following value as frontend url