Microsoft Exchange: Bug causes "[EXTERNAL]" in the mail subject line
Microsoft has apparently tweaked an Exchange function. As a result, "[EXTERNAL]" currently appears in the subject line.
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Anyone using Microsoft's Exchange server for mail traffic, for example within the Microsoft 365 package, may currently be receiving incorrect subject lines. Since midnight, numerous emails have started with the subject "[EXTERNAL]" – even in emails from colleagues within the same company.
A supposed quote from Microsoft support is circulating on Reddit: "We are currently investigating a recent code change to the 'Set-ExternalInOutlook' function that we suspect is responsible. To confirm this, we are collecting content traces of the affected email messages to identify the code that is causing the subject lines to unexpectedly contain '[EXTERNAL]'."
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Independent of settings and mail client
The bug also occurs when the external flag is completely deactivated. As it affects Microsoft Exchange, it also appears regardless of the mail client used, such as Outlook or Thunderbird.
Fixing the bug should be quite trivial for Microsoft. Users themselves can apparently do nothing about it at present.
(mma)
