Company url triggers outlook spamfilter

Hello!

At the beginning of this month, a percent of our company emails to customers started to end up in their spamfilter. It took us some research to find out that:

1. This happens only to customers using Outlook
2. This happens only when the company url is included, either in message text or in the sender email

Now, long before we narrowed this down to outlook, we checked our url in the spam filters around, it all came out ok. We also had a conversation with our email provider, as one of their smtp server ip's had a blacklist entry (for a long time we suspected this to be the issue), but this blacklist is of the unserious type and the listing was first created in 2004.

Then we started to check other options, and found out when sending emails from a gmail account to an account we knew to be handled by microsoft. Every time we sent an ordinary email with just random text, it ended up in the inbox. As soon as we included the company url, it went right to the spam folder. If we included the company name only (it's in the url), it went to the inbox.

So, from about March 4th and onwards, we can no longer trust our email communication with customers as we don't know which program they use to read it. If they use Outlook (or are in other ways part of the microsoft anti-spam regime), it will not go through. No other email programs/hosts seems to be affected by this.

It should be noted that the emails in question is sent by real people using an ordinary email program, in fact mostly Outlook. Our email policy is based on three ways of sending:

1. Order confirmation and order updates are sent by our web server

2. Requests to our sales email are mostly handled by the persons setting up orders

3. We do have a news letter option when registering, and uses mailchimp to send those emails app. once every two months

My thinking was that this had something to do with the recent spam flood to Outlook users, that started late February, but now I'm not sure. If our company url came back with a bad reputation when checking the spam blacklists, I'd understand the problem. But it does not, and it seems to be bound to the email program Outlook and only there.

Has anybody experienced something similar? And is it possible to contact microsoft to check what's going on?

Regards,
mog