From: windowsair Date: Tue, 15 Apr 2025 14:39:49 GMT Subject: RFC2822 Message-ID corrupted on some email servers when using git send-email Message-ID: <8771714B848C3A9F+9f64a309-ff70-466f-8d29-15950318b728@airkyi.com> Hi there! I am using `git send-email` to send emails and noticed a behavioral difference between different versions of Git. Since version v2.41.0, the Message-ID has been corrupted on my email provider exmail.qq.com. The broken Message-ID may be like this:         Message-ID: And in the early version, the normal Message-ID looks like this:         Message-ID: <20250415123238.17341-3-dev@airkyi.com> It appears that the email server is overriding this field. And I finally found this commit:         647a2bb3ffc0("Merge branch 'jc/spell-id-in-both-caps-in-message-id'") This commit consistently spell "Message-ID" as such, not "Message-Id". It seems that for my email server, using "Message-Id" results in the expected unmodified ID, while using the RFC2822-compliant "Message-ID" does not. So I want to document this here in case others encounter the same issue in the future :) Best regards, windowsair