TYPO3 Core

In 4.5 the class t3lib_formmail uses $GLOBALS['TYPO3_CONF_VARS']['SYS']['forceReturnPath'] which was previously only used in t3lib_htmlmail.

t3lib_formmail and t3lib_htmlmail use $GLOBALS['TYPO3_CONF_VARS']['SYS']['forceReturnPath'] in a different way. In htmlmail its only used as a flag to enable sending the return path. But in formmail its used also as the default return path

If your configuration is: $GLOBALS['TYPO3_CONF_VARS']['SYS']['forceReturnPath'] = 1;
t3lib_formmail will throw now an exception because 1 is not a invalid return path.

I think t3lib_formmail and t3lib_htmlmail should have the same behaviour for this configuration option.

Anyway the name forceReturnPath is quite confusing for what its used. I would split this up in three different configuration options:

sendReturnPath => enable/disable sending a returnpath
defaultReturnPath => a returnPath that can get overwriten
forceReturnPath => a returnPath that can not get overwritten

(issue imported from #M17575)