Why iCloud Mail is Slower Than Gmail

Gmail has a modern, efficient mail API

Gmail gives third-party apps a proper way to ask "what's new since I last checked?" Premail polls Gmail's History API every 10 seconds, and Google responds with exactly the new messages and nothing more. The whole thing completes in a fraction of a second.

iCloud uses an older mail protocol

Apple hasn't given third-party apps a modern REST API for iCloud Mail. Premail uses IMAP, which was designed in the 1980s. When the server supports it, Premail uses IMAP IDLE, which lets the server push a notification the moment new mail arrives. When IDLE isn't available, Premail falls back to polling every 5 seconds.

Either way, the round-trip overhead of an IMAP connection is higher than Gmail's History API. A single IMAP check can take several seconds if Apple's servers are slow, so iCloud mail typically gets processed a few seconds to a minute later than Gmail, depending on timing and server conditions.

If Apple's servers are temporarily unavailable, Premail waits progressively longer before retrying. This is protective behavior, but a flaky connection can cause noticeable delays.

What this means in practice

For most use cases, the difference is invisible. If a newsletter lands in your inbox and Premail archives it 40 seconds later instead of 5 seconds later, you are unlikely to notice or care. If you need near-real-time triage of time-sensitive email, Gmail will serve you better than iCloud for that purpose.