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Evolution-ews. Evolution did not seem to be as popular as Thunderbird. We found the interface to be of poor quality, and the configuration was complicated.
Thunderbird Cookie setting
There is a Thunderbird cookie setting which may be required:
The settings that were able to allow Owl to function are: (T’bird Settings -> Privacy & Security)
CHECK “Accept cookies from sites”
Accept third-party cookies: ALWAYS
Keep until: THEY EXPIRE