PDF Corrupted eM Client 8.1.979

Hello, hello!

With a very high probability there is a bug in eM Client when receiving PDFs with a icloud email account. Read more to find out why:

We have two clients with eM Client 8.1.979 installed. Both are running Windows 10 latest updates to date.

On one client we receive mails from different senders on a icloud.com account.

Some of these mails contain multiple PDFs. Some of these PDF are corrupted (Acrobat Reader - PDF Error Message). Same Error with Foxit Reader (corrupted or not a PDF). Some are not corrupted - even when received in the same email. Same happens of course also when

Forwarding these messages to the other client makes no difference.
Installing the same Mail account on both Windows 10 computers does not make any difference (still corrupted).

Opening the same files directly in icloud Webmail/Browser or downloading them from icloud Webmail to the Windows 10 client and open it with Acrobat is successful (no corruption).

Opening previously corrupted PDFs after forwarding the email in icloud Webmail to different Mail accounts of different providers (local Mailprovider, gmail, gmx) works fine.

PDFs in eM Client are still corrupted after forwarding the email from cloud Webmail to a different icloud account that is installed on eM Client.

Using the repair function in eM Client on the specific Mailaccount does not help (still corrupted).
No encryption are activated or installed in eM Client. No additional addons either.

With a very high probability there is a bug in eM Client when receiving PDFs with a icloud email account.

How can I solve the issue. It is super annoying as we receive plenty mails via icloud.

Best regards

There is a newer version of eM Client available for download from the Release History. Install that and see if there is any difference.

One thing you can also try is to save the pdf attachment, then open it from Explorer. Not a solution, but would be interesting to know the result.

Otherwise, best is if you have a Pro License to open a support ticket with eM Client.

Hi Gary

I just updated eM Client to 8.1.1032.

Same as before. ONLY messages received on icloud.com accounts show corrupted PDFs.

I also tested saving the pdf and opening to and from Windows File Explorer. No luck here.

To emphasize:
On Website icloud[dot]com --> receive mail with PDF --> download and open OR directly open PDF in internet browser —> WORKS PERFECTLY

On Website icloud[dot]com —> forward mail with PDF to e.g. gmail recipient —> in eM Client receive that said mail —> download and open OR directly open PDF in Acrobat ----> WORKS PERFECTLY

In eM Client —> receive mail with PDF on icloud account —> download and open OR directly open PDF in Acrobat —> DOES NOT WORK

There must be something buggy with icloud + eM Client.

Yes, I tried it with different PDFs from different senders. One is our provider that sends PDF invoices. These PDFs are impossible to open in eM Client. They can be opened on the icloud mail website or in Thunderbird Mail Client.

I now created different PDF files. X-4, X-3 and X-1.
X-3 and X-1 PDFs can be opened successfully everytime when received with eM Client and icloud or any other account.

But the PDF X-4 makes trouble in some random fashion.

I got a 100% corruption-rate when sending the X-4 PDF with eM Client from my gmail acocunt to my [email protected] mail address and receiving on eM Client.

No corruption when sending the X-4 PDF with eM Client from my gmail account to my [email protected] mail address and receiving on eM Client.
— but @me.com and @icloud.com are the same account ?!!

eM Client drives me crazy.

You could even say iCloud drives you crazy. :grin:

Indeed, yes. But is there a solution for my current issue?

This is something better discussed with eM Client. You’ve put a lot of effort into discovering where the issue lies, and it would be a shame just to see it end here.

Hmm… How do i get their attention? I thought eM Client is monitoring the forum…

Wondering if this opening .pdf file corrupted issue is because they are digitally signed ?

As i know there were issues prev in earlier eM Client V8.x with opening digitally signed with a SMIME certificate , that I believe was resolved with the recent versions of eM Client on pc and mac.

Yes. I wondered that too. I was able to recreate the bug with signed and non-signed PDFs.

Hello h2ox3,
it doesn’t matter if PDF file is signed. The question is whether e-mail is digitally signed (s/MIME). Can You see a signature badge and “Message is signed” in mail header under To: address?
Is the signature valid?

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It does not matter if it is s/MIME or not. The results were the same. Some of multiple attached PDFs on a mail were corrput. The rest of the PDFs were not corrupt. And again: it only happens when received on a icloud account installed in eM Client.

None of the attachments of the very same mail are not corrupted when opened in icloud webmail (NOT eM Client) or being forwarded by icloud webmail to an other non icloud account installed on eM Client.

And yes: the certificates are valid of the mails that were s/MIME.

We have identified the bug in iCloud server implementation of IMAP that causes this issue. The issue is that iCloud sends more and invalid data when chunk downloads (this is an IMAP protocol optimization) feature of IMAP is used. We’ll be able to workaround it in that way, that we’ll disable this chunk downloading for iCloud servers. However the bug is on iCloud side. We’ll try to make a build with this workaround as soon as possible. There is also a quick workaround for you even with the current version. Go to your iCloud account settings (Menu->Accounts), select Diagnosticts tab and put this parameter to Parameters (Advanced options) field: --imap-disable-chunked-download
And please let us know if it helped.


WOW! It seems to work. I forwarded 5 mails with troublesome PDF attachments from my icloud account to the same icloud account. Then I downloaded the mails in eM Client. I was able to open ALL PDFs without any trouble.


1 Like

Good news it helped. We’ll add that behavior for all iCloud accounts automatically as a workaround for the next releases. But please be aware that this is really a bug on iCloud’s side, not ours primarily.

The version that detects iCloud IMAP and automatically applies the workaround (disabling chunk download) is now available here:

Fantastic! I’ve installed the update and tested it. It seems to work fine. Super many thanks! Great support! :star: :star: :star: :star: :star: