Documentation - updated email setup (#10695)

* Updated email setup documentation to include sendmail option

* Update docs/content/doc/usage/email-setup.en-us.md

full path to sendmail

Co-Authored-By: mrsdizzie <[email protected]>

* Update docs/content/doc/usage/email-setup.en-us.md

docker image does not have sendmail

Co-Authored-By: Antoine GIRARD <[email protected]>

* Update docs/content/doc/usage/email-setup.en-us.md

Co-Authored-By: Antoine GIRARD <[email protected]>

* Update docs/content/doc/usage/email-setup.en-us.md

Co-Authored-By: James Lakin <[email protected]>

* Update docs/content/doc/usage/email-setup.en-us.md

Co-Authored-By: James Lakin <[email protected]>

Co-authored-by: 8ctopus <[email protected]>
Co-authored-by: mrsdizzie <[email protected]>
Co-authored-by: zeripath <[email protected]>
Co-authored-by: Antoine GIRARD <[email protected]>
Co-authored-by: James Lakin <[email protected]>

Author: 5 people

docs/content/doc/usage/email-setup.en-us.md

@@ -15,19 +15,33 @@ menu:
 
 # Email setup
 
-- To use Gitea's built-in Email support, update the `app.ini` config file [mailer] section:
+To use Gitea's built-in Email support, update the `app.ini` config file [mailer] section:
 
+## Sendmail version 
+Use the operating system’s sendmail command instead of SMTP. This is common on Linux servers.  
+Note: For use in the official Gitea Docker image, please configure with the SMTP version.
 ```ini
 [mailer]
-ENABLED = true
-HOST    = mail.mydomain.com:587
-FROM    = [email protected]
-USER    = [email protected]
-PASSWD  = `password`
+ENABLED       = true
+FROM          = [email protected]
+MAILER_TYPE   = sendmail
+SENDMAIL_PATH = /usr/sbin/sendmail
+```
+
+## SMTP version
+```ini
+[mailer]
+ENABLED        = true
+FROM           = [email protected]
+MAILER_TYPE    = smtp
+HOST           = mail.mydomain.com:587
+IS_TLS_ENABLED = true
+USER           = [email protected]
+PASSWD         = `password`
 ```
 
 - Restart Gitea for the configuration changes to take effect.
 
 - To send a test email to validate the settings, go to Gitea > Site Administration > Configuration > SMTP Mailer Configuration.
 
-For the full list of options check the [Config Cheat Sheet]({{< relref "doc/advanced/config-cheat-sheet.en-us.md" >}})
+For the full list of options check the [Config Cheat Sheet]({{< relref "doc/advanced/config-cheat-sheet.en-us.md" >}})