I have this plugin installed on a couple WordPress websites, running 4.1.1 and it works just fine. However, I do currently have send issues on WPMU installations. That being said…
If you are looking for a Newsletter plugin, for WordPress, that works with WPMU or a stand-along WordPress install, I suggest SendPress PRO (Bitly shortened link: https://bamajr.us/goSendPressPro).
SendPress is a FREE plugin (https://www.ads-software.com/plugins/sendpress/) for newsletters, but the PRO version has the ability to integrate your MandrillApp account, as the Sending Account. It has a very nice UI, its very easy to use and the support is great (NO, I don’t work for them).
Also, I believe MandrillApp is giving everyone a very generous 12000 free sent emails, per month (NO, I don’t work for them either). I think this makes SendPress Pro, with the Mandrill Sending Option, the best Newsletter solutions I’ve found, hands down (my opinion of course).
