No pdf attachment

From what could it depend that sometimes some pdf attachments cannot be opened?
Sometimes, when an email arrives with a pdf attachment, EMCLIENT tells me it can’t open or download it.
And since it only does it with some pdfs, I’d like to understand what it could depend on, also because if I try to download the same attachment with outlook, this is downloaded to me regularly.
Thanks a lot whoever wants to help me.

Could be todo with the pdf reader.

Try changing your OS default reader to a different one and then reboot your computer and try again. There is many freeware pdf readers out there.

If still a problem, could be the pdf files that won’t open have some sort of error in them which then won’t open.

It could also have to do with some error in the way your server parsed that attachment. You can right-click in the message body and choose Properties > Repair > Repair and when that is done, see if you can open the attachment.