Similar to this page, I was getting the following error:
ErrorDetail I/O Exception: peer not authenticated
Filecontent Connection Failure
Mimetype Unable to determine MIME type of file.
Statuscode Connection Failure. Status code unavailable.
Which you get when the JVM has an old version of an SSL certificate. More specifically, I was having problems connecting to ConstantContact, after noticing that they had just renewed their certificate:
Cracking my head open, and trying every solution in the world along what the people posted here, we just decided to reboot the server. This flushed the cache and it worked.
If you can afford to do this, then I recommend it if you want to go for the fastest solution. ConstantContact later provided other possible solutions.