Attachment file name with UTF-8 encoding seems to be broken

[maxfurioso]

Describe the bug Accessing the utf-8 encoded file name of an attachment returns a broken string. Please see the following image.

To Reproduce MimeMessage.Load() with such an encoded email.

Expected behavior The provided file name is correctly decoded.

Screenshots See above

Desktop (please complete the following information):

• OS: [e.g. iOS]
• Browser [e.g. chrome, safari]
• Version [e.g. 22]

Smartphone (please complete the following information):

• OS: Windows 11
• .NET 8
• Version 5.6.5

Additional context None