My experience with IMAP through a browser is helping friends install Thunderbird, friends who have had there account taken over in AOL, MS Mail and YaHoo.
When I install Thunderbird, I suggest to them that it does not require using a browser, greatly reducing the chance of being tripped up on <click here> websites.
Some have gone to POP, others have stayed with IMAP on Thunderbird and are very happy. The only reason they ever choose IMAP is synchronization.
In extending Thunderbird with this capability
1. Make secured e-mails without trusting the the server. Security ends
where trust starts. I trust Mozilla to produce a safe POP client and
trust LibreOffice would be in kind if they where to take it over.
2. Have Thunderbird POP installed on multiple devices that align
themselves to e-mail address(es) securely without the interaction of
a server except for PGP.
In regards to LibreOffice
1. Sharing document to online services in the cloud is OK, but why does
it have to be Google or Microsoft some other document sharing
service. People want to share their information within a limited
scope of addressees. If LibreOffice <File - Send - E-mail Document>
it is already leaning in that direction, why not push it a little more.
2. The graphical interface of LibreOffice has made some huge strides.
If LibreOffice took over Thunderbird, wouldn't it be great to have a
'Properties' panel on the right to e-mail.
3. If we already have <Edit - Track Changes - Record Changes>, why
shouldn't it push those changes to a pre-defined list of people
automatically via Thunderbird.
I just don't believe that because somebody else already did it, it couldn't done better and couldn't be done without a server. Probably more than 80% the of technology is already written in LibreOffice and Thunderbird. It is not starting from zero as has been implied.
Thank you for listening
Paul