All email clients I have used seem to update their message listings from the email server, but I don’t seem to get this working with Delta Chat. Not with two Delta Chat devices, and not with one Delta Chat and a normal Email program using the same email account.
Can’t Delta Chat list the emails that are currently on the server, and update that list for example after some messages got deleted using another device? I first noticed this with the contact requests, but it seems the same with the chat messages. I had expected that a new install would out-of-the-box be able to list the current messages that are on the server. And then continue to update the list if the messages on the server were edited, without any need to manually trigger any syncing or backup and restore action.
A backup/restore or transfer function may still be necessary to transfer a larger message archive without uploading to the server, but I think no email client has ever needed backup/restore/transfer, just to update the messages on another device.