Outlook for Mac (Classic) Keeps Re-downloading IMAP Emails from V-Hosting Server

Dear Francesco Manna, 

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First of all, thank you very much for providing such detailed information about the issue you are experiencing with Outlook for Mac (Classic interface) when using your IMAP email account hosted on V-Hosting. We completely understand how inconvenient and disruptive this can be, especially when you have to wait for thousands of emails to re-download every time you open the application. 

After carefully reviewing the information you provided, we would like to share our analysis of the root causes, address your questions, and suggest some practical solutions as follows: 

The phenomenon where Outlook continuously re-downloads all IMAP emails each time it starts is usually caused by several main factors: 

• The IMAP server may not consistently maintain technical identifiers such as UID/UIDVALIDITY – these are essential for Outlook to recognize which emails have already been downloaded. If these identifiers change (for example, due to moving folders, restoring backups, or simultaneous access from multiple apps), Outlook will treat all emails as new and re-download everything. 
• Outlook for Mac (Classic) has known limitations when working with standard IMAP servers (not Exchange or Gmail), especially with hosting providers like V-Hosting, which may not fully support all advanced IMAP standards required by Outlook. 
• Simultaneous access from multiple devices or apps (such as Apple Mail on iPhone) can sometimes alter the folder structure or UID status on the server, leading to synchronization conflicts in Outlook. 
• Corrupted cache or user data can also cause Outlook to lose track of previously downloaded emails, resulting in repeated downloads. 

I will answer each of your questions and together we will find the cause:

a. Could this be due to the IMAP server not supporting certain features Outlook requires?  → Yes, this is a common cause. If the server does not consistently maintain the necessary technical identifiers, Outlook cannot recognize previously downloaded emails and will re-download them each time. 

b. Is this a known issue between Outlook for Mac (Classic) and IMAP servers like V-Hosting?  → Yes, this is a well-documented issue on many tech forums. Outlook for Mac (Classic) is often unstable with standard IMAP servers, especially those provided by hosting services that are not Exchange or Gmail. 

c. Would switching to REST or using a different email client prevent this behavior?  → Possibly. However, the "New Outlook" for Mac currently only supports Exchange, and Outlook.com, and does not support custom IMAP accounts. If you use third-party software/app, or Outlook for Windows, these clients are generally more stable with IMAP. For long-term use of Outlook, we recommend considering Exchange Online for maximum compatibility. 

Based on your information, I can give you some steps to check whether the issue still occurs or not: 

a. Please try using webmail:  We recommend logging in to your V-Hosting webmail via your browser. Webmail connects directly to the server and is not affected by local IMAP sync issues, so it’s a great way to check if the problem is server-related or just with Outlook. 

• If webmail works smoothly and you don’t see emails reloading or duplicating, the issue is likely specific to Outlook for Mac. 
• If you notice similar problems (such as slowness, errors, or emails reloading/duplicating) even in webmail, the specific cause may be with the server itself, and you may want to contact V-Hosting support for further investigation. 

b. Limit folder changes from multiple devices:  When using Outlook (or any email client), we recommend avoiding frequent moving, deleting, or reorganizing of email folders from different devices at the same time, as this can sometimes cause IMAP sync issues. 

c. Try another email client:  If possible, try accessing your account with third-party software/app. If these clients work fine and don’t re-download emails every time, it further suggests the issue is with Outlook for Mac (Classic). 

d. Contact V-Hosting:  We recommend reaching out to V-Hosting to confirm whether their IMAP server fully supports UID/UIDVALIDITY and does not reset these identifiers when changes occur. 

e. Consider switching to a more professional email service:  If you need to use Outlook reliably in the long term, you might consider migrating to Exchange Online, which are fully supported by Outlook and offer more stable syncing. 

Your feedback will help us pinpoint the issue and suggest the most effective solution. 

We look forward to your response and are ready to provide further assistance if needed. If you require step-by-step guidance for any of the above checks, or if you have any other questions, please do not hesitate to contact us. We are always here to support you. 

Thank you very much for your trust and for using our services!

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