minor #15241 [Mailer] Added link to https://symfony.com/doc/current/mailer.html#configuring… (ThomasLandauer)

This PR was merged into the 5.2 branch.

Discussion
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[Mailer] Added link to https://symfony.com/doc/current/mailer.html#configuring…

…-emails-globally

https://symfony.com/doc/current/mailer.html#configuring-emails-globally

Question: If I add a From-header here, and then use a different `$email->from(...)` in the code, which will win? Since "envelope" has an unusual behavior in this regard, it might be better to explain this here too.

Commits
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4836e5d Added link to https://symfony.com/doc/current/mailer.html#configuring-emails-globally

Author: javiereguiluz

reference/configuration/framework.rst

@@ -3213,6 +3213,10 @@ headers
 Headers to add to emails. The key (``name`` attribute in xml format) is the
 header name and value the header value.
 
+.. seealso::
+
+    For more information, see :ref:`Configuring Emails Globally <mailer-configure-email-globally>`
+
 web_link
 ~~~~~~~~