Just committed an update to the leenk.me plugin. I've had a couple reports from users with old version of cURL who could not post to leenk.me because it could not verify the SSL certificate. Without going into too much detail, the SSL certificate I purchased for leenk.me is a new and old web browsers may not know how to verify the trusted source, this includes old version of cURL.
The only way around this is to tell WordPress to not worry about verifying the SSL certificate when it communicated with leenk.me. The content will still be encrypted and sent without a problem, it is just automatically trusted.
If you run into any issues, let me know.