Cannot preview txt and html email attachments in Outlook 2019 x64

Copper Contributor

when I try to preview a txt or html attachment in Outlook 2019 x64 (on Win 10 20H2 x64) email I've got an error:

This file cannot be previewed because of an error with the following previewer:
Windows TXT previewer (Html Previewer)
To open this file in its own program, double-click it.


And it is ok with xlsx, docx, pdf and images previews.

PreviewHandlers key is in the Registry and seems to be ok.

Also I have no previews at all (blank preview without any text, except images and videos) in Explorer Preview pane (for what it's worth).

1 Reply

Finally I've found the solution (for all extensions having associated preview handlers in registry).
I had 64-bit Preview Handler Surrogate Host registry key missing in HKCR\AppID section, but did have 32-bit version.
So I recreated 64-bit version similarly to 32-bit key.


@="Preview Handler Surrogate Host"


From that point all the previews in Outlook desktop (2019) and in Preview pane in Windows Explorer started working, no need to restart (Explorer or Windows).