If the MS 365 SPF setup fails, mimetals.com addresses may not be able to reach some external email domains.
View the MS domains page here, to see config and status - https://admin.microsoft.com/Adminportal/Home?source=applauncher#/Domains/Details/mimetals.com
Failures under the Nameservers section will cause SPF to fail. As instructed by the Microsoft error, the values from this Nameserver section need to be copied over to the external DNS registrar for mimetals.com - https://www.networksolutions.com/my-account/home