Sent mails from iPhone only visible on IPhone - same for Drafts

The easiest way to repair an issue with an IMAP account is to log into their online portal and ensure that everything is on the server, then delete the account from the phone, and then add it back again, ensuring that it is configuring as an IMAP account and correctly verifies. I would restart the iPhone after deleting it and before adding it back again.

Just to add some more info to this issue, which affects me as well.

• First noticed in early March, 2025, on the then-current version of iOS. Still present today, on the current version.
• Impacts the Sent and Draft folders, as in this thread's initial description.
• Intermittent. Goes away around the 10th of the month, and comes back around the 1st of the next month. Which is crazy.
• Impacts iOS only. Apple Mail on (latest) MacOS is fine. I don't have an iPad to test.
• Only reproducible on Apple Mail. Outlook for iOS and Edison Mail are both fine.
• Out of three phones (SE 2016 w/ latest iOS 15.x, SE 2022 w/ latest iOS 18.x, 15 w/ latest iOS 18.x), only the two running 18 have the issue. All three tested with the same IMAP account, on the same server. I don't have another account or another server to test.
• Fully resetting the phone (the 15 in this case) to a minimal state (i.e. without importing anything from another phone or the cloud or anything), then only setting up the mail account allows to reproduce the issue. Account creation is done through the "other" option, since the supplier isn't one of the major ones. IMAP, not POP3.
• The original post refers to a thread that says to change the server folder. I can't test: changing the folder isn't persisted on the phone (applying the change and then coming back to re-check it results in the original folder being shown as the active one). I consider this to be a second, distinct issue.
• Reported to Apple Support. No solution.

I'm failing to find another explanation than a bug in Apple Mail.

Its is not clear from your iPhone is the issue is with iOS mail app or some third-party apps.

• Some third-party apps (e.g., Outlook, Spark, Gmail) may save drafts locally first and sync only after a delay or when hitting "Save."
• Temporary network issues or app bugs might also cause drafts to remain unsynced for a while, even with internet access.

Whether a draft email stays on the iPhone or gets synced to the server depends on:

Email Provider and Protocol

• IMAP (most common today: Gmail, iCloud, Outlook, Yahoo, etc.):
  • Drafts usually sync to the server automatically if the device has internet access.
  • You can start a draft on your iPhone, finish it on your laptop, and vice versa.
• POP3 (older, less common):
  • Drafts are stored locally on the device and not synced to the server.