Are you an Amazon Associate? Do you use their affiliate links in your email list? Or on your blog? If you do then you could be violating their terms of service
Section 4 states this
4. Promotional Limitations
You will not engage in any promotional, marketing, or other advertising activities on behalf of us or our affiliates, or in connection with an Amazon Site or the Associates Program, that are not expressly permitted under the Agreement. You will not engage in any promotional, marketing, or other advertising activities in any offline manner, including by using any of our or our affiliates’ trademarks or logos (including any Amazon Mark), any Program Content, or any Special Link in connection with email, offline promotion or in any offline manner (e.g., in any printed material, ebook, mailing, or attachment to email, or other document, or any oral solicitation).
And then section 5 prohibits Amazon associate links in apps too.
The problem comes for bloggers where some of your readers subscribe to your feed by email. Either through a service they subscribe to you or one that you provide.
I’ve just created a WordPress plugin that strips the Amazon Associate tags and link codes out of links in your RSS feed and any email sent by your WordPress site itself. It has a simple settings page where you add all your associates tags and the plugin takes care of all your Amazon links whether they are text/image, image, text or amzn.to.
It’s available here. You are welcome!