Looking through their API docs, one of the things that I noticed is that they added a transaction log (&quot;delta&quot; field), which IMAP doesn&#x27;t have: <a href="https:&#x2F;&#x2F;www.nylas.com&#x2F;docs&#x2F;#deltas" rel="nofollow">https:&#x2F;&#x2F;www.nylas.com&#x2F;docs&#x2F;#deltas</a><p>Having a server communicate with IMAP (which is slow), cache the results, and export a more efficient&#x2F;log-structured alternative probably makes syncing client computers much faster.