My wife runs a small website (in Japanese) selling vintage products online. She's sending out emails to customers with details about their order, together with images of the products and links to the item page(s).
All emails go via postmark (a credible 3rd party email delivery service). We also use SPF and DKIM to make sure emails are not flagged as spam. Most emails arrive without a problem, with a very low bounce-rate. As far as my wife and her customers are concerned, the emails are totally legit.
Occasionally however, when customers reply to one of those emails, we see a subject line that looks something like this:
RE: [***Spam***](Suspicious Urls) ご注文ありがとうございます。 - Frau Vintage
From looking at the email headers, I believe this is emailed from MS Outlook (
X-Mailer: Microsoft Office Outlook 12.0). Is this something done by Outlook's embedded junk e-mail filter, or perhaps third-party software?
Does anyone know which spam filter or tool marks those emails as spam and perhaps which method it uses to classify URLs as "suspicious"? Is there a way for my wife to report these as false-positives to the vendor?
Note: unfortunately it is not an option to contact the email recipient directly or ask them to take any action. This will most likely scare them or cause unnecessary confusion, so I would like to investigate this without any customer assistance.