[Users] Firefox, Chromium won't open HTML mail

[Pierre A.]

> Something's not really clear to me: you don't really have * in the
> file:// URIs, do you?

Anyway, my theory was wrong.

File names that Firefox or Chromium do not like: 

/home/alba/.claws-mail/mimetmp/0000000b.mimetmp.html
/home/alba/.claws-mail/mimetmp/00000006.mimetmp.html
/home/alba/.toto/0000000d.mimetmp.html

File names that Firefox or Chromium do like: 

/home/alba/Desktop/0000000b.mimetmp.html
/home/alba/Desktop/mimetmp/00000006.mimetmp.html
/home/alba/toto/0000000d.mimetmp.html

I now infer that Firefox or Chromium can't open "hidden" files.

The problem is not in Claws Mail but Claws Mail happens to be my only occasion to see it.  I don't know why this appeared suddenly.  

I don't think it is a problem in Firefox since it is also in Chromium and both programs are independent.

Maybe some wrong setting in my Ubuntu.