This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Attachments displaying as "size unknown"

  • 5 replies
  • 2 have this problem
  • 1 view
  • Last reply by wordword

more options

It's been a few weeks now that majority of my incoming and outgoing attachments display as "size unknown" and cannot be opened. My thunderbird is version 52.3.0. Some attachments sent from an email on the same host go through, others do not. For example, an email coming from a Gmail account to my custom host--the attachment says "size unknown" and I cannot download it. When I log into my email via the host, it's all there. So this is a Thunderbird issue for sure.

It's been a few weeks now that majority of my incoming and outgoing attachments display as "size unknown" and cannot be opened. My thunderbird is version 52.3.0. Some attachments sent from an email on the same host go through, others do not. For example, an email coming from a Gmail account to my custom host--the attachment says "size unknown" and I cannot download it. When I log into my email via the host, it's all there. So this is a Thunderbird issue for sure.

All Replies (5)

more options

got an anti virus scanning you incoming mail? Try disabling it and see if the attachments appear then as they download. It is unfortunately fairly common for anti virus products to completely scramble attachments. Particularly PDF files.

more options

I tried disabling my AVG for an hour, that didn't seem to help. Any other ideas?

more options

If you open Tools/Options/Advanced/General/Config. editor and double-click (toggle) the preference mail.server.default.fetch_by_chunks to false, OK, and restart TB, does it make any difference with received attachments?

more options

sfhowes said

If you open Tools/Options/Advanced/General/Config. editor and double-click (toggle) the preference mail.server.default.fetch_by_chunks to false, OK, and restart TB, does it make any difference with received attachments?

No, attachments still say "Size Unknown"

more options

Matt said

got an anti virus scanning you incoming mail? Try disabling it and see if the attachments appear then as they download. It is unfortunately fairly common for anti virus products to completely scramble attachments. Particularly PDF files.

Disabling my scanning (AVG) didn't seem to help. Any other ideas?