SpamAssassin marking mailings as compromised WordPress site
Can you detail out some more information.   Without the filter added there is no change at all to mailings pre and post civicrm 5.25.   The urls are the same until you add the filter.   I am unsure how to evaluate without a list of the URLs they are dinging you for and I understand you would not want to post them here.  As far as the REST API for mailing, you can try this https://develop.tadpole.cc/plugins/cv-rest-mailing  it's a small plugin that implements the filter needed.