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I created a filter in Thunderbird 14 on client A that, when a certain rule on incoming mail is satisfied, the same mail is forwarded to client B and C.

Matching mails received from A are always forwarded to B and C, and that's what I want. Though, when the mail on A has an attachment, it is also forwarded by B and C but the file they receive is corrupted. In my case the incoming file on A is a Word file of about 10kb in size; clients B and C receive a Word file of 27 bytes.

I think this could happen because the forward starts from A when the attachment is not yet completely downloaded. I'm not sure this is the cause, though. And I wouldn't have any idea for a fix.

Any idea about how to investigate or solve the issue?

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I had the same error reported above, in case anyone else is experiencing this here is the error and the fix!

Error: Created a filter to forward new messages with attachements, email is sent with attachements which are created but are only 27 bytes and do not open properly.

Fix: Found in Comment #65 on

Go into Tools-->Options-->Advanced-->Config Editor

mail.imap.mime_parts_on_demand : true -> false mail.server.default.mime_parts_on_demand : true -> false

Also check to see that these settings match mine:

Go into Tools-->Options-->Composition

Forward messages: Inline Add extension to file name: Unchecked

Hope this resolves your issue as it did mine.

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This is a bug in Thunderbird. It seems to be an old issue that some users have seen on several versions of Thundbird over the last few years. The bug reports seem quite long and confused, so it's likely a hard to reproduce bug.

You should upgrade to the newest version of Thunderbird (currently 16) if possible.

If this doesn't solve the problem you should review the following bugs and perhaps try to add any additional information (like the mail server you are using) to help the free, open source project fix the issue:

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Thanks for your answer. It's a problem, though. I have some workaround in mind and then report what I did in case of success. – Paolo Nov 14 '12 at 12:54
Not really happy but I found a fix moving the rule from client A server side. The forward is done thus by the mail server. – Paolo Nov 15 '12 at 22:53

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