From what I can see, Lemon is "a blockchain" 
which can also speak IMAP/SMTP over servers when required. Sorry, but there is no way to send a valid e-mail without a valid e-mail server. The website is incredibly shady about that. I can understand why.
Security by obscurity, huh? Come on, trust them! 
-Tuxman
Finally we're getting somewhere.
I appreciate your perspective because you are technically knowledgeable, make really good points based on your knowledge and experience, and have insights that I lack. I just wish you'd make your good points in the first place instead of abrasively trolling multiple times before the real information finally gets teased out of you.
My understanding of Lemon is that it is a new paradigm on email. It provides similar functionality in a similar format, but with some differences in the underlying technology. It stores the encrypted content of the messages in IPFS format, which allows it to be duplicated and decentralized on the IPFS network. It
uses a blockchain (Ethereum) to store metadata (e.g., the IPFS hash) about the messages. And it provides an account system which messages are tied to and sent to/from. I imagine that Lemon to Lemon messages don't use SMTP/IMAP/POP3 at all. But because they offer (what I'll refer to as) "backward compatibility" with traditional email software/servers, they also provide as part of their service something that interfaces with SMTP so that you
can send to and receive from other SMTP accounts. But that is optional if you and the people you want to communicate with are using Lemon and don't need to communicate with others outside of the Lemon ecosystem.
That is to say, they provide two different services:
1. A traditional web-based & mobile client service similar to Gmail and other mail services, or optionally your own email client using SMTP/IMAP. This does indeed have a server for account management and SMTP stuff.
2. A fully decentralized app (DApp) with no central server, and seemingly no server at all. This is still in testing and being developed. In theory, even if Lemon goes out of business, this version of the service could live on in perpetuity. But I'm not sure how or if it could communicate with traditional email addresses at that stage.
Indeed, as you said, the main Lemon website seems scarce with the details, but there's a lot
more information about the DApp version of Lemon here as well as in the
open source Github repository.
Yes, Lemon is still new to me, and I'm still looking into the details of how it works, so my explanation(s) above may not be entirely accurate. Given that the source is open, and you're free to deploy it yourself, I think your quip about "security through obscurity" is baseless. There's no need to trust them if you don't want to. You can verify for yourself what the software is doing by perusing the code. In fact, I encourage you to do that. It isn't my intention to mislead anyone about what this is or how it works. But you don't have take my word for what it is or how it works. Look into it yourself, if you feel so inclined, and (politely) point out where I'm wrong.
