I am looking for an email client. It can be destkop or web app too.
I manage five emails on three computers, so it would be good if it would have a feature like "setting sync".
Syncing in both directions is one of the key features of the IMAP protocol for arbitrary folders. For example in Thunderbird you can additionally define the synchronization options per account and folder, if they should be always downloaded etc. This allows to have the emails in sync everywhere and optionally still on the devices themselves.