Only Amazon can do that...... But that explanation must fall within the bounds of it's privacy policy. Personally, the only emails that I ever receive from Amazon are those that are absolutely necessary to carry out transactions but I am very careful about the boxes that I tick.

The best that I can suggest here for the moment is to install DNT+ and see if that helps.

I went to look at the 'usage' and privacy policy stuff (Thanks Deadbeat!) and these paragraphs are interesting:

Automatic Information: we receive and store certain types of information whenever you interact with us. For example, like many websites, we use "cookies" and we obtain certain types of information when your Web browser accesses Amazon.co.uk or advertisements and other content served by or on behalf of Amazon.co.uk on other Web sites. Click here to see examples of the information we receive.

Automatic Information

Examples of the information we collect and analyse include: the Internet protocol (IP) address used to connect your computer to the Internet; login; e-mail address; password; computer and connection information such as browser type and version; and time zone setting, browser plug-in types and versions; operating system and platform; purchase history, which we sometimes aggregate with similar information from other customers to create features such as Best Sellers; the full Uniform Resource Locators (URL) clickstream to, through and from our website (including date and time); cookie number; products you viewed or searched for; and any phone number used to call our customer service number. We may also use browser data such as cookies, Flash cookies (also known as Flash Local Shared Objects), or similar data on certain parts of our website for fraud prevention and other purposes. During some visits we may use software tools such as JavaScript to measure and collect session information, including page response times, download errors, length of visits to certain pages, page interaction information (such as scrolling, clicks, and mouse-overs), and methods used to browse away from the page.We may also collect technical information to help us identify your device for fraud prevention and diagnostic purposes

Information from Other Sources

Examples of information we receive from other sources include: updated delivery and address information from our carriers or other third parties, which we use to correct our records and deliver your next purchase or communication more easily; account information, purchase or redemption information and page-view information from some merchants with which we operate co-branded businesses or for which we provide technical, fulfillment, advertising or other services; search term and search result information from some searches conducted through the Web search features offered by our subsidiary, Alexa Internet; search results and links, including paid listings (such as Sponsored Links); and credit history information from credit bureaus, which we use to help prevent and detect fraud and to offer certain credit or financial services to some customers.

To me, it indicates that they do get information from other sites.

I don't ever recall opting to receive marketing emails, and with any site, if there's a button to opt in/out of info sharing, I always opt out.

At least, seeing hypertony gets the same, I'm not the only one seeing this on occasion.

All that's pretty standard and expected; all to do with offering goods and fulfilling your orders.

In reply to a post by TrishaH:

To me, it indicates that they do get information from other sites.

I still don't see how that covers them knowing you browsed eBay. eBay is not a supplier or carrier of your Amazon orders; more a competitor.

I see no button on Amazon to opt out of marketing (looked under My Profile) but then I don't expect one as I never get marketing from them.

I thought it may mean they have partners or associated sellers on Ebay. Can't say I've noticed any Amazon links or otherwise on Ebay, but some companies seem to get everywhere.

I got a marketing email from Amazon earlier - something I've browsed on both sites though, but at the bottom in tiny print, there's a section to unsubscribe:

We hope you enjoyed receiving this message. However, if you'd rather not receive future e-mails of this sort from Amazon.co.uk please opt-out here.

..so I did
It took me to a page on Amazon, and the first button seemed to relate only to the items in the email, but I noticed another button to opt out of all such communications. Next time, I'll use that.

Was it from same Amazon email addy?

I am also seeing the same thing from Halfords too.

In reply to a post by XRaySpeX:

Was it from same Amazon email addy?

Yes, the same one.

In reply to a post by hypertony:

I am also seeing the same thing from Halfords too.

Must be some sort of information sharing thing we see now and then.

It really does feel like we can do very little without it going on record or noted in some way!

Never got any of those marketing emails despite browsing your item on both sites 3 days ago

Good!

It's not often it happens with me, so perhaps could be a randomly chosen thing ...who knows!
It's obviously not 'dangerous', just irritating.