TYPO3: How to restrict the file upload in Powermail with the file formats

I am using powermail where I have added a file upload which I want to restrict with PNG,JPG and PDF file formats. Since I unfortunately do not work as long as TYPO3 and the extension Powermail I do not know exactly where I have to make the changes. I have already seen in another forum post that you can make the adjustments in the setup.

plugin.tx_powermail.settings.setup.receiver.overwrite{
   upload.file_extensions = jpg,png,pdf
}

Best regards

Solution

You can configure the allowed fileextension as TypoScript constant plugin.tx_powermail.misc.uploadFileExtensions.

So, the TypoScript (in constant section) should look like:

plugin.tx_powermail.misc {
   uploadFileExtensions = jpg,png,pdf
}

file_extensions seems to be a configuration value years ago (The mentioned post was from 2011), but does not exist in the current powermail code.