I've set up a semi-automatic email (using an HTML template) that gets sent out of SF in certain situations by an apex trigger.  This works as it should.

Problem is, I'm finding that MS Outlook, using its default settings, will mark the email as Junk (spam).  I want to avoid that.

I already turned on the SF deliverability options.  That by itself didn't solve the problem, but probably reduced the junk "score" that Outlook assigns.

Further testing: this template contains both an image (header on the email letterhead) and a number of links, pointing to the client's website.  I've found that if I remove either the links or the image, Outlook accepts it.  But with both if them in there, it calls it junk.

We generally don't have this problem w/ emails sent by services like Vertical Response.  (Maybe because the links in that case are redirects which first go to VR's domain, so the domain of the links & the email are the same??)  But we can't use VR for this, since the emails are triggered.

Any advice on how to improve deliverability here?  I've heard about the option of using our own mail server instead of SF's, but I don't think that's going to be feasible for this client.  Anyone got other ideas, and/or good resources for understanding how Outlook's junk filter works?

Thanks much!