Then, Roundcube became the standard.
Their dominance is being eroded by Mailpile, RainLoop, and Nylas.
Around the edges, we have Peps, Mailr & Kite which may all someday take off.
Zimbra and the well known groupware vendors (OnlyOffice, Horde, Citadel, Kolab) are competing in more-or-less the same space.
Probably dozens of other projects that are on the same level that I have never even heard of.
I would love some sort of comparison, even a biased one written by the respective teams.
Anyone have useful links?