Fighting invisible devil in MIME mail

I came across a strange behavior when trying to create and send MIME mail.

The mail body content is set in LS code from the stream with UTF-8 encoding and contains just formatted text and some URLs, pointing to the doc in the same db, nothing unusual. Most of the time it works just fine. But sometimes I see extra white space inserted here and there. It may be in the linked text which doesn’t look good but at least it doesn’t break the link. But it also may appear in the url itself, which is totally unacceptable. It happenes with the web mail only. The latest stats goes like that:

out of 25 e-mails retrieved from Hotmail/IE8 a few had this, out of 25 e-mails sent to Gmail/FF one had this. None for mail in Notes client.

In all these cases extra white space appeared in the linked text, but I also saw it in the URL itself in some previous testing.

Question: 1) anybody saw this behaviour for links in the MIME e-mail? 2)what may have caused it?

I’d appericiate your thoughts and suggestions.