HTML e-mails to this list are silently dropped?

["SebA" <spa (at) syntec.co.uk>]

I was trying to send e-mail to this list and they were being silently
dropped rather than published.  I changed my e-mail format from HTML to
Plain Text and - hey, presto - my e-mail is not dropped!  Trying this e-mail
in HTML format first to see if it reproducible on a simpler message (without
tabs and numbering)...  If this is published, it points to tabs or numbering
being disliked by the mail program.  If it is not published, further
evidence that HTML containing e-mails are dropped...

Regards,

SebA