diff --git a/custom/conf/app.example.ini b/custom/conf/app.example.ini
index c4d5413a6c2..4ea658dac2a 100644
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@@ -1533,6 +1533,7 @@ PATH =
 ;SENDMAIL_PATH = sendmail
 ;;
 ;; Specify any extra sendmail arguments
+;; WARNING: if your sendmail program interprets options you should set this to "--" or terminate these args with "--"
 ;SENDMAIL_ARGS =
 ;;
 ;; Timeout for Sendmail
diff --git a/docs/content/doc/advanced/config-cheat-sheet.en-us.md b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
index 2fbfdde6bd6..043c7e0d43c 100644
--- a/docs/content/doc/advanced/config-cheat-sheet.en-us.md
+++ b/docs/content/doc/advanced/config-cheat-sheet.en-us.md
@@ -666,7 +666,7 @@ Define allowed algorithms and their minimum key length (use -1 to disable a type
    - Enabling dummy will ignore all settings except `ENABLED`, `SUBJECT_PREFIX` and `FROM`.
 - `SENDMAIL_PATH`: **sendmail**: The location of sendmail on the operating system (can be
    command or full path).
-- `SENDMAIL_ARGS`: **_empty_**: Specify any extra sendmail arguments.
+- `SENDMAIL_ARGS`: **_empty_**: Specify any extra sendmail arguments. (NOTE: you should be aware that email addresses can look like options - if your `sendmail` command takes options you must set the option terminator `--`)
 - `SENDMAIL_TIMEOUT`: **5m**: default timeout for sending email through sendmail
 - `SENDMAIL_CONVERT_CRLF`: **true**: Most versions of sendmail prefer LF line endings rather than CRLF line endings. Set this to false if your version of sendmail requires CRLF line endings.
 - `SEND_BUFFER_LEN`: **100**: Buffer length of mailing queue. **DEPRECATED** use `LENGTH` in `[queue.mailer]`
diff --git a/docs/content/doc/usage/email-setup.en-us.md b/docs/content/doc/usage/email-setup.en-us.md
index 390dc78e506..df1b8545af5 100644
--- a/docs/content/doc/usage/email-setup.en-us.md
+++ b/docs/content/doc/usage/email-setup.en-us.md
@@ -35,6 +35,7 @@ ENABLED       = true
 FROM          = gitea@mydomain.com
 MAILER_TYPE   = sendmail
 SENDMAIL_PATH = /usr/sbin/sendmail
+SENDMAIL_ARGS = "--" ; most "sendmail" programs take options, "--" will prevent an email address being interpreted as an option.
 ```
 
 ## Using SMTP