Are there any good cloud-based email clients?

In need for #cloud #email #client --> https://www.google.com/search?q=cloud+email+client

Think "ThunderBird for the cloud" --> http://forums.mozillazine.org/viewtopic.php?p=11509055&sid=4f36eacd9f9262efa238ca00d176ca59#p11509055 --> "I'm also interested in a ThunderBird cloud service. There is the other practical issue which is I have several email accounts and not all of them are with Google."

Nice to have: - 2-step auth - open source - mobile app (mobile first design) - reliability - labels / filters / priorities

Are there any active projects in that field? --> would like to issue pull request, send money on kickstarter or just talk with founders... Generally, how people solve this issue these days?

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### Current workflow: I own domains and have catch-all feature forwarding all incoming messages to intermediate gmail account.

### Issue: when hitting "reply" it gets messy - https://support.google.com/mail/answer/22370?hl=en-GB&ctx=mail - kind of works but I would like something more robust (and not breaking ToS), designed from the ground up for 20+ email accounts.

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Thank you for any suggestions!