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Hi.
Problem solved, I am just posting the solution to help others.
I had the same problem like at this post: https://projectdmc.org/support/topic/attached-files-are-not-sent-anymore/
WP Version 6.4.3
ContactForm7 Version 5.9
Contact Form 7 Multilingual Version 1.2.2
MailPoet Version 4.44.1
The solution was deleting MailPoet.
I observed that MailPoet overwrote the email headers sent from ContactForm7, it added things like sendingservice.net to Return-Path