Thai text in meeting invite bodies shows as garbled characters on one PC (classic Outlook, new Outlook and web), but displays correctly on another laptop Problem Thai text in the BODY of meeting invitations/cancellations from one external sender

Export the same affected invitation from Outlook on the web on both computers and compare its raw MIME content; this will determine whether the mailbox contains corrupted text or the affected PC is rendering identical stored data incorrectly.

1. Compare the stored invitation

On each computer:

1. Open the same invitation in Outlook on the web.
2. Select More actions (…) → Download. Outlook saves the item as an .eml or .msg file, normally in Downloads.^1^
3. Keep the files separately, such as invite-bad.eml and invite-good.eml.
4. Compare their hashes from PowerShell:

$files = ".\invite-bad.eml", ".\invite-good.eml"
$files | ForEach-Object {
    Get-FileHash $_ -Algorithm SHA256 |
        Select-Object Path, Hash
}

Then open both files in a text editor and inspect the MIME sections containing:

• Content-Type: text/calendar
• Content-Type: text/html
• charset=
• Content-Transfer-Encoding:
• DESCRIPTION:
• The first Thai text that becomes garbled

Outlook treats imported iMIP calendar data as UTF-8 even if the text/calendar part declares another charset. It can also replace the calendar DESCRIPTION with the first text/html child of a multipart/alternative section.^2^ That behavior makes the sender’s generated calendar/HTML MIME parts—potentially including the Zoom template—the primary content to inspect.

Interpret the result as follows:

• Thai is already garbled in both raw files: the damaged or incorrectly encoded content is stored in the mailbox. The receiving PC’s Outlook encoding settings cannot restore characters that have already been converted.
• Thai is valid in both raw files, but only one PC displays it incorrectly: this is a local rendering/parsing problem on that PC, not Exchange Online modifying the stored body.
• The files differ: retain both files and their message headers for Microsoft support. Also verify that both downloads are the exact same calendar item and update.

2. Check the documented sender-side condition

Microsoft documents a closely matching Outlook problem affecting meeting requests: strange mixed-language characters can be generated when the sender’s Windows device has Beta: Use Unicode UTF-8 for worldwide language support enabled. Outlook does not support that setting for these generated items.^3^

This is applicable only if that option is enabled on the external sender’s computer. Ask the sender to check:

1. Settings → Time & Language → Language
2. Under Related settings, open Administrative language settings.
3. Under Language for non-Unicode programs, select Change system locale.
4. If Beta: Use Unicode UTF-8 for worldwide language support is selected, clear it.
5. Restart Windows.
6. Create and send a new test invitation.

This prevents corruption in newly generated items; it does not repair invitations already received.

Why only meeting bodies are affected

Meeting invitations are not handled exactly like ordinary email. Internet calendar data uses text/calendar, while the human-readable body can be carried in alternative HTML or plain-text MIME parts. Outlook may select the HTML part as the meeting description.^2^

Exchange can also transport Outlook-specific meeting information through TNEF or standards-based MIME. MIME supports non-ASCII character sets; TNEF packages Outlook features such as meeting requests.^4^ Consequently, ordinary email from the sender can be correct while calendar messages produced by their scheduling or Zoom integration are malformed.

Exchange Online and the device difference

There is no Microsoft-published known issue in the supplied known-issues material that specifically matches Thai meeting bodies in Version 2610 Build 16.0.20527.20150.^5^

Because classic Outlook, new Outlook, and the web client fail on one PC while the laptop succeeds, a classic-Outlook-only profile or add-in problem is unlikely. If the exported MIME is identical, investigate the affected PC’s browser profile, Windows text/font components, and endpoint security content inspection rather than changing Outlook encoding again.

An Exchange message trace can show receipt, delivery, and processing events, including related records and mail-flow activity, but it does not prove which raw Thai bytes were present before and after processing.^6^ For escalation, provide Microsoft Support with:

• One affected .eml
• One rare correctly rendered .eml from the same sender
• Screenshots from both computers
• Message IDs and timestamps
• The sender’s meeting-generation client and Zoom integration version
• Confirmation of whether the sender’s beta UTF-8 system-locale option was enabled

References

1. [Web](https://support.microsoft.com/outlook/mail/save-an-outlook-message-as-a-eml-file-a-pdf-file-or-as-a-draft)
2. 2.2.168 [RFC6047] Section 2.4 Content-Type Header Field
3. Strange characters are displayed in meeting requests, read receipts, and IRM messages
4. Message format and transmission in Exchange Online
5. Fixes or workarounds for recent issues in classic Outlook for Windows ...
6. Message trace in the Exchange admin center in Exchange Online