Powermail plugin gathers all mail informations from other plugins on the same page by sending the mail
If you have two or more powermail plugins on a page, that use the same form, and you fill a form and send, powermail plugin gathers SenderMail, SenderName, Subject, RecieverMail, ReceiverName, Subject from another plugins with same form on the same page and then send mails to all of them.
This happens at least on the version 10.8.0.
Yes, I have two or three forms on the page. I made different markers in the forms on purpose. This worked at least in TYPO3 11. All the forms on the page submitted normally. After switching to TYPO3 12, the version of powermail changed accordingly. And the forms stopped being sent if there is another (different) form on the same page.
@aksenovaa Your issue is solved with commit 896cdabb5a5de7c0a0f1a2379192d84f6643aadc