Outlook 2010 receives HTML as Plain Text

[Leif]

I have an odd situation where I am receiving a HTML formatted email OK, but another user on the same network receives the same email in plain text, with the 'extra line breaks removed message', and it begins with:

--_010_4C0C33E0A6070D4692839683796F4B381863B581BL2PRD0712MB630_
Content-Type: multipart/related;

boundary="_009_4C0C33E0A6070D4692839683796F4B381863B581BL2PRD0712MB630_";
type="multipart/alternative"

--_009_4C0C33E0A6070D4692839683796F4B381863B581BL2PRD0712MB630_
Content-Type: multipart/alternative;

boundary="_000_4C0C33E0A6070D4692839683796F4B381863B581BL2PRD0712MB630_"

--_000_4C0C33E0A6070D4692839683796F4B381863B581BL2PRD0712MB630_
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable

Both PC's running Outlook 2010. The message had another message as an attachment, and multiple links in the signature. As this message came in to a generic mailbox and then delivered to multiple mailboxes, I can't see that it was sent in different formats. On the 'offending' machine, it was received in the Inbox, not Junk folder.

Has anyone any ideas where to start looking for a solution?

Edited to add:
Other HTML-formatted emails are being received OK, so it is not an total 'convert all HTML to Plain Text' issue.

[HansV]

Does that user have his or her antivirus program set to scan e-mails? I found some reports that this may cause *some* messages to be converted to plain text.

[Leif]

Ah, yes! Kaspersky, and we are running different versions (don't ask... ) Let me see what I can find out from that.

Thanks!

(Interestingly, if I forward my correctly formatted copy, it is received OK.)