We rely on providers for pull sync functions, providers have limitations, these include:
- Timeouts for open connections
- Limits on throughput
- Limits on number of IP's with simultaneous connections
- Usage of services
However additionally the performance of the provider has a bearing on the sync speeds, IMAP is without a doubt the oldest, slowest protocol, being provided by 100's of different providers, each with their own custom infrastructure.
Nylas can't resolve periodic delays in syncing of objects.
We are at the mercy of the provider, there is little we can do to improve provider performance, please feel free to reach out to support should you see continuous delays or missing objects.
Our suggestion: Use a more reliable provider, or move away from single threaded IMAP protocols.
We are aware of ongoing performance issues with Yahoo and Zoho.