Some sort of unified inbox / folder view would be great. The idea is that you can see at the first sight whether or not you have new mails in any of your accounts.

To complete this excellent tool, a calendar could be great to be used as a simple PIM for a small entity to send and receive appointments.

Either this calendar is in CalDAV format to be connected via a mobile phone (Android, Ios...) or uses a remote CalDav calendar provided by another open system.

To sum up, the same system you did for CardDav contacts but for events.

Once again, good job.

Thanks

Please add a global search feature, to search mails in all folders.
Many imap clients do this (squirrelmail, K9-mail, thunderbird...). Even if slow or ineffective, it can be sometimes useful to find a very old mail when using multiple folders.

The possibility to assign contacts to (multiple) groups

Not sieve filters, just regular filters created as a plugin written in php (there are similar plugins for other webmail platforms) and they do not need sieve integration or stuff like that..

A global address book, to share contacts between several users.

It would be great if you could add the CardDAV contact images in addition to the gravatar option.

I was wondering if it could be possible to have openpgp encryption/signing by default if the recipients have keys imported in Rainloop.

It would be nice for people like me who always want to encrypt and sign their emails whenever their recipients will be able to use that information.

You should be able to change the email sorting order.

It woud be nice if you could implement in addition to PGP s/mime support.
s/mime for encrypted messages and s/mime for digital signature

Thank you

It would be great to assign email lables

Relating to Owncloud integration, possibility to sync multiple address books

Because SPF ( https://en.wikipedia.org/wiki/Sender_Policy_Framework ) some mails would be marked as SPAM. If you cannot configure SPF you need to use smtp server from same domain as identity.

Like in AfterLogic Webmail (as rainloop have similar design) it will be great to have a quick reply form in the bottom of the message:

Screenshot: http://goo.gl/Zi4FRD

Hi. I would like an option to list all unread messages on top (if multiple, sord by date). After the unread, list the read emails, sorted by date.

Ability to access a contact directory stored in LDAP and add/delete/update it.

A way to add "message templates" or whatever they may be called and add them to a new message (they might also work as signatures).