Test 4 involves a tabbed table, and a collapsible section. As usual, I'm using ugly colors to distinguish between different table cells. This time I wanted to see the difference between the Domino generated HTML, and the iFidelity generated HTML, so I tried it both ways.
My environment is still Lotus Domino 8.5, with Lotus Notes 8.5, and the mails are sent to my Google mail account, which is set to forward all mail to my Notes mail. This is tested with iFidelity beta 1c.
So, the original mail sent from Notes looked like this (each tab has the same text):
Google mail, Domino generated:

The grey twisty icon to the left of "Collapsible section" is not clickable at all.
Google mail, iFidelity generated:

The red down arrow isn't clickable in any way.
Notes mail, via Google mail, Domino generated:

The grey twisty icon to the left of "Collapsible section" is still not clickable at all.
Notes mail, via Google mail, iFidelity generated:

The red down arrow still isn't clickable in any way.
All things considered, both do the job, even if I think iFidelity makes nicer tabs in Google mail. On the other hand, It would be nice if thay were preserved on incoming mail in Notes as well.
The collapsible section icons feels reduntant in both renderings, since thay aren't really collapsible any longer. The SMTP receiving end doesn't necessarily know anything about Notes' capability of collapsible sections. The important thing here is that the section title is kept intact, which it does both ways.