Forum notifications for followed threads not formatted correctly in Thunderbird

[Granddaddy]

I can't find an appropriate place to post this problem, so I'm posting here as the least inappropriate place.

The problem:

I receive in Thunderbird e-mail client several notifications telling me there are new posts in threads I am following in the Affinity forums. A few of those e-mails display as HTML source code instead of displaying as fully formatted HTML mail messages. Of course this makes them largely unreadable.

At the beginning of the e-mail message is a link to the post in question. Here's just one example from this morning:
Go to this Post: https://forum.affinity.serif.com/index.php?/topic/173835-what-ergonomic-design-principles-call-for-minimal-contrast-and-reduced-readability-in-user-interfaces/&do=findComment&comment=1002868

Notice the &amp: strings in the final section of the link. Clicking on the link will take me to the first post in the thread. Deleting the two amp: strings from the link (retaining the &) will take me directly to the post.

Perhaps someone can explain what might be happening, why this happens with only two or three e-mail messages out of 7 or 8 that might arrive together.

The problem is not thread specific. It might happen with any thread I am following. It might happen with one notification from a particular thread and not with another notification from that same thread received at the same time.

I do not see this happening with any other e-mail messages I get from any other source. Only the notifications of a new post in a followed thread in the Affinity forums exhibit this behavior. If it is a Thunderbird bug, then why does the problem not occur with other HTML mail I receive from dozens of sources? If it is a Forum bug, then why doesn't it happen with all e-mail I receive from the forums?

Is a puzzlement to me.

[Corgi]

I haven't noticed this, perhaps because I have Thunderbird displaying emails as HTML (View => Message Body As... => Original HTML). The page displays correctly, and those links seem to work correctly in HTML mode. 

[Granddaddy]

Thanks for your quick reply.

Yes, I have Thunderbird set to display message body as Original HTML. 

The problem is confined to random notifications from the forums. I get tons of other HTML mail from dozens of senders and never have a problem. Also, the majority of notifications from the forums are fine. But this morning, 40% of notifications failed to format. 

My first guess was that something is missing or being stripped off the e-mail headers somewhere along the way.

I'm just looking at two different notifications of posts you made to the Communication and Secrecy thread this morning. The notification for one of your posts formatted correctly. The notification for a second post did not format and all I get is the HTML source code.

Looking at the mail headers with View Message Source I see that the e-mail that fails to format is missing a dozen or more headers that do appear in the correctly formatted notification. In particular the To:, From:, Subject: headers are missing along with a bunch of others that are meaningless to me including Authentication-Results, DKIM-Signature, MIME-Version, Content-Type and some others.

Perhaps Xfinity is messing things up somehow. 

But again, I have no problems with any other HTML e-mail messages, only with random notifications from the forums.

[Corgi]

Very odd. Well, I'm only one data point, but I've never seen any issues in forum notifications on Thunderbird.

[Granddaddy]

Thanks for taking the time to reply. I guess it helps to know it is not a widespread or common problem. 

I haven't found such a problem reported in searching for Thunderbird issues in general. 

I screen a lot of my mail each morning using the native iPad mail as an iMap client. What I don't delete at that time, I receive later on my desktop computer using Thunderbird as a POP client. The iPad mail client never fails to format the mail correctly.

For now it remains a mystery. In writing this it occurs to me that I should use a web browser before downloading the mail and see what changes I observe. But that gets to be tedious and time consuming to figure out a problem I can live with. The notifications are not something I save.

As my mother often said: Oh well. What can you do? You just have to put up with it I guess.