[TASK] respect sender.default.senderEmail for sender mail TO fallback

[jpmschuler]

In current powermail 8.4.1 I have a form with empty settings.flexform.sender.email (yay editors) and sender mail enabled. Now the email is send to the server admin email address (dunno taken from which setting yet).

For the recipient email I can define the

• FROM with plugin.tx_powermail.settings.setup.receiver.default.senderEmail and the
• TO with plugin.tx_powermail.settings.setup.receiver.email

For the sender email doing the same the

• FROM is plugin.tx_powermail.settings.setup.sender.email and
• plugin.tx_powermail.settings.setup.sender.default.senderEmail gets ignored thus the TO falls back to my server admin email address.

The code shows a lookup for senderName but not for senderEmail, thus I propose to copy that code for senderEmail, too.

[jpmschuler]

closed as more detailed tests fail, will reopen as soon as stable