Relax from check (#277)

* Relax from check

- Print a warning instead of an error, if envelope_from is set.
- In case of an error, provide a hint about envelope_from.

* Potential fix for pull request finding

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

main.js

@@ -147,7 +147,14 @@ async function main() {
         // Either: "Plain Simple Name <user@doma.in>" or just "user@doma.in" (without the <>)
         let parsed = addressparser(from);
         if (parsed.length != 1 || parsed[0].address == '') {
-            throw new Error("'from' address is invalid");
+            // Report an error only if the user did not set envelope_from. Otherwise, envelope_from
+            // overrides from anyway and from is used as is (but Nodemailer will remove
+            // the From: header completely).
+            if (envelopeFrom) {
+                core.warning("'from' address is invalid. Nodemailer will not create a 'From:' header.");
+            } else {
+                throw new Error("'from' address is invalid. Maybe you want to set 'envelope_from' to a valid sender address?");
+            }
         }
 
         // if neither to, cc or bcc is provided, throw error