I’m seeing the same using smtp against zimbra on the newest version of emclient (7.0.27943.0)
edit: it was the zimbra with airsync, that they do not support. I see normal behavior when using smtp/imap. Frustrating setup on the emclient. autodiscover insists on ews (that dosent work good with zimbra&emclient). Please get something better for zimbra support.
https://forum.emclient.com/emclient/topics/zimbra-support