Let's say that John Smith at XYZ Corp has authored a paper. The company obviously wants recognition and so they use their corporate email address "jsmith@xyz.com".
John has since moved on and is earning more at ABC Corp instead. XYZ Corp has duly reclaimed John's old email address, and John cannot receive emails at said address any longer.
This is the situation the OP is in. It was never a "fake email address". They did not literally type "first.last@org", that was an example suitable for using in their comment.
[edit: I'm actually wrong with that last statement, as it turns out. While it wasn't a fake email address, the situation is slightly more nuanced in that OP actually did say "{first}.{last}@hhi.fraunhofer.de" in the paper, as there were multiple authors who all had the same email address format - see https://news.ycombinator.com/item?id=41479618. I still think this is a valid method, though, and it's certainly not fake. Besides, the problem I outlined sounds like it probably remains an issue even if it's not the exact problem OP is experiencing.]
Ok, so they used a template on the paper, namely "{first}.{last}@hhi.fraunhofer.de", while the email addresses, if the names are applied to the template, do in fact yield valid email addresses.
It sounded as if they were using "john.doe@hhi.fraunhofer.de" while in reality it was an invalid email address ("because there’s no match with the email address"), that he would have tried to claim co-authorship via his "real" address, which might be something like "j.doe2@hhi.fraunhofer.de" (but luckily is not).
It's all clear now. Thank you for your explanation.
This is what I was asking about and I thank you and GP for clarifying the situation. There also send to be an unnecessary flamewar about the impermanence of email addresses generally, that's an unfortunate accident.
John has since moved on and is earning more at ABC Corp instead. XYZ Corp has duly reclaimed John's old email address, and John cannot receive emails at said address any longer.
This is the situation the OP is in. It was never a "fake email address". They did not literally type "first.last@org", that was an example suitable for using in their comment.
[edit: I'm actually wrong with that last statement, as it turns out. While it wasn't a fake email address, the situation is slightly more nuanced in that OP actually did say "{first}.{last}@hhi.fraunhofer.de" in the paper, as there were multiple authors who all had the same email address format - see https://news.ycombinator.com/item?id=41479618. I still think this is a valid method, though, and it's certainly not fake. Besides, the problem I outlined sounds like it probably remains an issue even if it's not the exact problem OP is experiencing.]