Continuing my attempts to reproduce this under Linux Mint 17.3, I went and grabbed TB 52.0, from here:
https://ftp.mozilla.org/pub/thunderbird/releases/52.0/linux-x86_64/en-US/thunderbird-52.0.tar.bz2
I tested replying to an email through davmail+office365, it worked as expected.
TB updated itself to 52.2.1, and I tested the same reply, and it worked as expected.
I don't have convenient access to a Win7 64-bit machine, so I can't attempt to reproduce this on that platform at the moment.
Continuing my attempts to reproduce this under Linux Mint 17.3, I went and grabbed TB 52.0, from here:
https:/ /ftp.mozilla. org/pub/ thunderbird/ releases/ 52.0/linux- x86_64/ en-US/thunderbi rd-52.0. tar.bz2
I tested replying to an email through davmail+office365, it worked as expected.
TB updated itself to 52.2.1, and I tested the same reply, and it worked as expected.
I don't have convenient access to a Win7 64-bit machine, so I can't attempt to reproduce this on that platform at the moment.