When I asked how to figure out how outlook filter junk email, I was always
treated as one who want to send spam email, ok , I understand that.

But the situation is this, I send email for my clients, send from their
domains. These emails are not spam.

Ok, that doesn't matter neither, here is the strange problem, I send one
email to my account. It goes into my outlook inbox, which works fine. Now I
edit the email body in a htmleditor, and then send an email with the edited
content, it ends up in junk box. So I did a lot of testing, compare the
content to see when it goes into junk box. I found many things could trigger
that, like changing of the subject etc. I tried to keep the change as minor
as possible. Guess what I found, there are two places, if I change span
style="font-size :11pt;" to span style="font-size :11pt", the email will
go to junk email. so just two semi-colon, and outlook treats it differently.

As I said, I send email for my clients, I can not tell all receiver to add
the sender email as safe sender. And when using any htmleditor, under IE, IE
DOM will create html like span style="font-size :11pt", not span
style="font-size :11pt;". If I run htmleditor on FF, I do get html like
span style="font-size :11pt;"

So here is the situation, a block of source html, if I send it to outlook,
it will go to inbox, it is not treated as a spam. Once I edit it in
htmleditor under IE, after it goes through IE DOM, some css will be changed
by IE DOM even I don't change anything myself. Then it will be treated as
spam in outlook.

Any suggestion?

thanks