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From: Dirk Fieldhouse <surname@gmx.net.removethisandtherest.example.com>
Newsgroups: alt.comp.software.seamonkey
Subject: Reading email as plain text
Date: Fri, 10 Dec 2021 16:20:54 +0000
Organization: Speaking personally
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For those who like to read email in plain text, with actual link URLs 
exposed, etc, SM (and TB, though maybe not in the GUI of recent versions 
- I haven't checked) offer more facilities than you might think.

 From the SM GUI (View>Message Body As...) you can choose to view 
messages as Plaintext, Simple HTML, or Original HTML. This is a global 
setting; sadly, changing it in separate message window persists across 
the whole application.

One might wonder what "Simple HTML" is. The details are explained by the 
developer <https://www.bucksch.org/1/projects/mozilla/108153/> (expired 
cert):

In the table below, "html_as" specified the transformation applied to 
the HTML part, and "disallow_mime_handlers" specifies the stringency of 
stripping potentially nasty content from the HTML, unless overridden by 
a higher global setting.

> UI option	        pref values (mailnews.display.*)
> 	   prefer_plaintext	html_as	disallow_mime_handlers
> Original HTML	false   	0	0 (no HTML)
> Simple HTML	false   	3	1 (strip using built-in list)
> Plaintext	true    	1	1

Ben explains that "Simple HTML" is generated by converting the "Original 
HTML" to plain text with a sort of Markdown-like formatting and then 
converting it back to HTML. The aim is to strip out potentially 
dangerous links. The conversion process is described here 
<https://www.bucksch.org/1/projects/mozilla/16507/>.

This is great, but there's one issue. A lot of corporate email comes 
with a deliberately useless plaintext alternative part that says 
something like "To show this message as we want, open this link in your 
browser". In such a case one would like to force the display of the HTML 
part as converted to plaintext, but (apart from manually deleting the 
plaintext part using an add-on like "Header Tools Lite") the only option 
in the GUI is to switch to Simple HTML to read the email, and then back 
again. The add-on "Allow HTML Temp" used to enable a one-time switch but 
no longer works in 2.53.10+.

Ben explains that there is a config option combination to help:

mailnews.display.
	prefer_plaintext	false
	html_as        		1

With these settings an HTML alternative part, if present, should be 
shown after converting to formatted plain text; otherwise the plaintext 
part should be shown. This works just as if the plaintext alternative to 
an HTML part was deleted.

Now the problem is that the GUI doesn't recognise this combination of 
settings, which gets nuked if one of the "View>Message Body As" options 
is selected.

Finally, going back to 
<https://www.seamonkey-project.org/releases/seamonkey2.6/changes>:

> Attachments in emails with certain structures or encodings may not be shown in the attachment pane. Set the mailnews.display.show_all_body_parts_menu pref to true in about:config, then select View/Message Body As/All Body Parts to make such attachments available (BZ 677905).

But unfortunately "All Body Parts" corresponds to "html_as" = 4, so 
enabling and using this item also nukes the "prefer_plaintext=false, 
html_as=1" combination.

If an add-on (or a patch to the source) were to enable that combination 
in the "View>Message Body As" menu, what should it called?

"Textified HTML"?
"HTML As Plaintext"?
"Elucidated HTML" (made plain!)?

/df

-- 
London
UK