Seems like either my server’s DNS management is entirely bust or WordPress/Automattic/Akismet changed something their end, because as discussed yesterday in my cannot resolve downloads.wordpress.org and dashboard (RSS) empty post, the fix is rather straight forward:
add the needed IPs and the corresponding hostname to /etc/hosts (on the server, not local client!),
you can see how to do it in the before mentioned post.
You can get the akismet IPs yourself by pinging rest.akismet.com or just check their website and FAQ at http://blog.akismet.com/akismet-hosting-faq
Just use the first one:
72.233.69.3
72.233.69.2
66.135.58.62
66.135.58.61