Hi,

I am writing to report a critical and recurring failure in IMAP connectivity following the Build 9540 and 9543 updates. Our investigation shows that your 'security hardening' and 'RFC compliance' changes have severely broken Outlook integration for power users.

We have identified two specific triggers for this failure:

Mailbox Size: Accounts with 5GB+ data are consistently failing.

Folder Complexity: Even small accounts (e.g., 300MB) are hanging if they utilize a large number of IMAP folders.

The most frustrating part is that re-creating the Outlook profile is NOT a permanent solution. Even after a clean profile setup and full resync, the connection stays stable for only 3 to 4 hours before it falls back into the same 'Send/Receive' hang. The client simply stops receiving responses from the server and stays in a permanent 'Not Responding' state during synchronization.

It is unacceptable that a paid enterprise solution like SmarterMail is currently outperformed by free, open-source alternatives like Dovecot, which handles these exact same accounts and folder structures without any protocol exceptions or hangs.

We cannot continue to force our customers to perform manual OST surgery every 3 hours. We need an immediate fix for the IMAP command-handling logic that is causing these sessions to freeze.

(Customers outlook versions: 2019-2025 Turkish. Outlook Classic and Outlook new mixed)
(This issue isn't just happening with one customer; it's happening with around 30-40 customers)
Outlook version change not fixed this issue.