Hmm. After upgrading to 10.2.5 and Safari v73, I get this error frequently when Mail.app checks my hotmail. I am also using the most recent http hotmail plugin for Mail.app (v.1.17). I can manually check mail fine, and I don't get this error all the time. But it has happend several times tonight (after updating Safari). I've already repaired permissions and rebooted twice. What's the problem?