Apple Mail: View/Message/All Headers is grey and unusable

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It will help us get a good idea of what is causing your problem if you provide a report of your system, that way we do not have to play 20 questions with you. The report we are requesting does NOT provide any personal information and is extremely safe to use. Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211 It is helpful to us if you download the report to your Desktop.

Restart the computer in Safe Mode and restart normally and test it.

If the "View/Message/All Headers" option in Apple Mail is greyed out and unusable, it might be due to the specific email message you are currently viewing. Here are a few troubleshooting steps you can try:

1. Select a Different Email: Try selecting a different email message within your mailbox. The "View/Message/All Headers" option may only be available for certain types of messages, such as those that contain more detailed headers.
2. Ensure Proper Selection: Make sure you have the email message selected or opened in the Mail app. If the message is not actively selected, some options may appear greyed out or unavailable.
3. Check Message Format: Verify that the email you are trying to view headers for is in the proper format. Some email messages, such as plain text messages or messages from specific email services, may not provide the option to view all headers.
4. Enable All Headers: If the option is consistently greyed out for all messages, you can check your Mail preferences to ensure that the "All Headers" option is enabled. Go to the "Mail" menu, choose "Preferences," select the "Viewing" tab, and ensure that the "Show header detail" or similar option is checked.
5. Restart Apple Mail: Quit the Apple Mail application and relaunch it. Sometimes, software glitches or temporary issues can cause certain options to become unavailable. Restarting the application may help resolve the problem.
6. Update Apple Mail: Ensure that you are running the latest version of Apple Mail. Updating your Mail app to the latest available version can help fix bugs and improve functionality.
7. Try a Different Email Client: If the issue persists and you require the ability to view all headers frequently, you might consider using an alternative email client that offers more comprehensive header options. There are various third-party email apps available for macOS that provide advanced header viewing capabilities.

If none of these steps resolve the issue, it could be a limitation or configuration specific to your email account or server. In such cases, you may need to consult with your email service provider or system administrator for further assistance.