Standalone Web Client for Multiple IMAP Accounts?

[consultant]

I currently use Thunderbird as I have multiple e-mail accounts and I like to use IMAP instead of POP3 as then I can have folders within each email account and those folders are server based rather than client-machine based.

I have a couple Gmail accounts too.  Thunderbird is rumored to only continue development into mid 2013.  I think Mozilla has officially dropped it or something to that effect.

I prefer web-based e-mail clients anyway as then my e-mail experience is consistent no matter where I access it from.  Just need a browser. 

The problem is, all these services, Gmail, Outlook.com, Zoho, etc. only allow you to add external accounts as POP3.  Why is there no web-based client that allows you to access external e-mail via IMAP. 

Ideally I want a web service that allows me to see all my inboxes for a all accounts in a unified folder (like you can do in Thunderbird, but NOT in Outlook 2013 - which is surprising - but that's Microsoft trying to chain you to their server products - Exchange - for more advanced features.) 

The only thing I've found that comes even close to doing this is web2mail personal account.  But the interface is really rudimentary.  No unified inbox.  Folders are in a drop down list rather than a tree on the left. (What can you expect for free though I guess.)

Everything else is a client/server product.  Meaning you have to install a server component on the actual email server which servers the web-based interface.  But I've got multiple accounts on multiple servers.

Seems like it should be easy to add ability for Gmail to read accounts via IMAP and have the accounts and their folder tree added to the left side of the screen and give an option for a unified inbox view.

Any tools/ways to do this?  Anything better than mail2web out there that doesn't require installation of a server component?

[Yoni]

For Roundcube Webmail we have the accounts plugin. From your single Roundcube Webmail account, you can check many other accounts on remote servers as long as those servers offer IMAP support without even login out from your Roundcube session. It can be configured to allow connection to specific hosts, all hosts or even assign hosts per user.

Irrespective the limitations from which we can talk in deep for webmail clients to offer an unified mailbox, there is also the fact that many admins may not like having their server used as a mail client for other domains or services other than theirs.

[mikea]

We don't have. It is a commercial plugin.

Open-source should not hide the cost of things. It is understood it is not free as in free beer, but free as in open. However, when mentioning commercial plugins, it should be noted also that its is as such. Otherwise people waste time researching when that may not be what they want.