For a number of reasons, I’ve kept my AOL email account, but have naturally incorporated it into a single mailbox using fetchmail and AOL’s imap interface. I noticed that fetchmail started doing this all of a sudden:
fetchmail: Server certificate verification error: unable to get local issuer certificate
fetchmail: Server certificate verification error: certificate not trusted
After some investigation, it appears that fetchmail is suddenly having trouble negotiating a TLS connection via IMAP. Beats me why — it either didn’t make the attempt before or something has gone funny on the AOL side — but aside from being vaguely annoying, it turns out that the mail still gets through, and these errors effectively mean nothing whatsoever.