minor #12872 SMimeEncrypter add Tip (zairigimad)

This PR was submitted for the 5.0 branch but it was squashed and merged into the 4.4 branch instead (closes #12872).

Discussion
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SMimeEncrypter add Tip

Add Tip about SmimeEncrypter to configure cipher.

Commits
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4874152 SMimeEncrypter add Tip

Author: javiereguiluz

mailer.rst

@@ -656,6 +656,11 @@ and it will select the appropriate certificate depending on the ``To`` option::
     $firstEncryptedEmail = $encrypter->encrypt($firstEmail);
     $secondEncryptedEmail = $encrypter->encrypt($secondEmail);
 
+.. tip::
+
+    The ``SMimeEncrypter`` class defines a second argument to choose
+    an algorithm to encrypt the message. the cipher must be one of these PHP constants: https://www.php.net/manual/en/openssl.ciphers.php
+    
 Sending Messages Async
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