Still an issue under iOS 18.4. My company maintains their own email servers using Dovecot for IMAP. So far we have iOS 18 IMAP issues with only one of our clients. In this case a user with a really really large list of IMAP folders (5503 in total). It takes multiple days before the folders are even shown under iOS and INBOX synchronisation takes ages. Deleting and re-adding the email account does not work. Tested under iOS 18.3 and iOS 18.4. This was not an issue under versions of iOS before iOS 18.