On my Zimbra Pro OVHcloud mailbox, the preview of PDF attachments fails with the message “Unable to load preview”.
The problem occurs on Windows, Android, macOS and iPhone/iPad, including in webmail. By contrast, image‑format attachments display correctly. PDFs can be downloaded and opened on the computer.
The issue therefore appears to be specific to PDF preview.
Good morning @eric
Zimbra's PDF viewer has trouble processing large files or files with many pages. I suppose you get a message that says “Unable to load preview” – Download.
To rule out that this is what I'm describing, let's do a test: send yourself an email with a PDF that contains one single page and we'll verify if it displays correctly.
Let me know, best regards.
Sergio Turpín
Hello, the test was performed with a single page. The result is identical with the error message “unable to load the preview”. It’s the same on all devices: Android, iOS (iPhone, Mac, iPad), Windows, and the web version. Have a great day. Eric
Hi @eric
I did a test on my side with a one‑page PDF and it works fine for me. That doesn’t mean your problem doesn’t exist; OVHcloud has several Zimbra servers, and your account might be on one where the preview service is failing.
Since the error occurs on all devices, the most effective thing is to open a ticket with support, indicating which Zimbra server you are using (you can see it in the email headers) and attaching the PDF that fails. That way they can reproduce the error and check the specific server.
Let us know, cheers.
Sergio Turpín
Which server to use? I have zimbra1....
Hi, I created simple PDF files and the result is the same.
Hi @eric
The host zimbra1.mail.ovh.net resolves to a single IP, but OVHcloud may be load‑balancing or serving different customers from different nodes.
What’s most useful isn’t the webmail host’s IP, but the Message-ID of one of your emails. The value that appears after the @ in that line identifies the server or domain associated with your mailbox, and that’s what support needs to locate your specific case.
I recommend that you open a ticket with support so they can give you more detailed information about this:
Click this link to create a support request from the OVHcloud Help Center. Then, log in with your OVHcloud credentials.
Once you have logged in, click ✉ Tickets on the Ticket creation button. Select the reason for your request and then the product and service in question. Then, specify your request to get personalized help suggestions and advice. If this does not meet your needs, click Next to complete your request and create a support ticket. Be sure to provide as much information as possible so our teams can help you better.
Keep us informed 
Sergio Turpín
Thank you. I’m forwarding the information I just retrieved in the message.
Hello,
I have just created a ticket with the message ID of an email that has an attachment causing problems. Is there anything else I can do to resolve this issue?
Thank you
Hello everyone,
This issue is known internally, the mail teams have been working on it since the end of September. For now, unfortunately you have to wait 
Astérix