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• Always add tests
• Keep backward compatibility (see https://symfony.com/bc).
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Review the GitHub status checks of your pull request and try to solve the reported issues. If some tests are failing, try to see if they are failing because of this change.

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Cheers!

Carsonbot

The change has been done on purpose, see #37888 for the explanation.

I'm sorry, but I don't understand why in #37888 this change is made. What is wrong with setting the sender via the return path if it is set? Btw other mailers do it this way.

In my opinion this will be correct -- first: "sender", second: "return-path", last: "from"

private static function getSenderFromHeaders(Headers $headers): Address
    {
        if ($sender = $headers->get('Sender')) {
            return $sender->getAddress();
        }
        
        if ($return = $headers->get('Return-Path')) {
            return $return->getAddress();
        }
        
        if ($from = $headers->get('From')) {
            return $from->getAddresses()[0];
        }

        throw new LogicException('Unable to determine the sender of the message.');
    }