Redirect (3XX) URL in XML Sitemaps
This means that the URL in question returns an HTTP 'Redirect' status (3XX), yet is included in an XML Sitemap.
Why is this important?
Your XML Sitemap should only contain URLs you wish for search engines to index. URLs in your sitemaps should be clean - i.e. sitemaps should only include URLs that are HTTP status 200 (OK), indexable, canonical and unique.
If search engines find 'dirt' in sitemaps, such as 301 pages, they may stop trusting the sitemaps for crawling and indexing signals. This causes extra work for search engines and presents a conflicting message about which URL 'should' be indexed.
Eric Enge once interviewed Duane Forrester while he was at Bing;
What does the Hint check?
This Hint will trigger for any internal URL which returns an HTTP status of 3XX, and is included in one of the submitted XML Sitemaps.
Examples that trigger this Hint:
Consider the URL: https://example.com/page-a, which is included in a submitted XML Sitemap.
The Hint would trigger for this URL if it had a 301 (Permanent Redirect) header response:
Similarly, URLs with other 'redirect' statuses will trigger the Hint (i.e. any other 3XX response).
How do you resolve this issue?
To resolve this issue, simply remove any URLs that return 3XX from all XML Sitemaps, and replace them with the destination URL instead (if the destination URL is not already included in the sitemap).