Attachment file name are renamed to other attached file name sending from Outlook 2010.

※ この記事は下記の英訳になります。
Title : Outlook 2010 で 複数ファイルを添付し送信すると、添付ファイル名が別の添付ファイルの名前に変更されてしまう (ファイル名が入れ替わる)

※ This article is English translation of below.
Title : Outlook 2010 で 複数ファイルを添付し送信すると、添付ファイル名が別の添付ファイルの名前に変更されてしまう (ファイル名が入れ替わる)

Update :
This issue was fixed by KB3114570.
Title : January 12, 2016, update for Outlook 2010 (KB3114570)

When multiple attached files are sent from Outlook 2010, attached files name are re-named to other attached file name.
In addition, when the extension is also re-named, the file is unable to open with the error.

This issue occurs when matching below two criterial:

1. Outlook 2010 which has applied below update:

   Title : August 11, 2015, update for Outlook 2010 (KB3055041)
   URL :

2. When multiple files are sent as attached file.

This issue does not always repro even the above conditions are applied.

How to check if KB 3055041 is installed:
1. Start Outlook 2010.
2. Click [File] tab.
3. Click [Help].
4. Click [Additional Version and Copyright Information] on the right side of dialog.
5. Check the numbers that are next to “Microsoft(R) Outlook(R) 2010” on the dialog.
if your Outlook build number is over 14.0.7155.5000, then KB3055041  has already been installed.

Repro Steps:
1. Create a new message, type some text in message body, subject, and add someone on the To line.
2. Attach multiple files to the message.
3. Press [CTRL]+[S] or click [Save] on the quick access tool bar but don’t close the Inspector.
4. Send the message.
5. Check sent item or received item.

When the following attached files are sent, the file names including extension are swapped and the attached files are unable to open.
An Excel file of BBBBBB0123.xlsx and a Word file of BBBB0124.docx are swapped include extension.

Original file is Word format, but file names including extension are swapped.
In this case, the current file format is Excel, so Excel will try to start when you double click the file, but original format is Word, so the file is unable to open.
Please kindly ask the original file names including extension to the sender and modify them to the correct file name and extension.

Original file name                        Swapped file name
AAAAAAAAAA.txt                        AAAAAAAAAA.txt
BBBBBB0123.xlsx                       BBBBBB0124.docx
BBBBBB0124.docx                      BBBBBB0123.xlsx

Microsoft has confirmed that this is a problem.
Outlook team update this blog when any information is updated or fix is published.

For now, there are some way to prevent this issue.


(1) Close and re-open the message when it is save to Draft folder.
This issue occurs when the message item is save to [Draft] folder.
We confirmed that the issue does not occurs with the following steps.

– Steps
1. Click [Draft] folder.
Check if the message with multiple attachments is saved to [Draft] folder.
2. When the message is saved to [Draft] folder, take the following steps to save the latest contents.
Press [CTRL]+[S] or click [Save] on the quick access tool bar
3. Close the message with [X] (close) on the right corner of the message window.
4. Re-open the message which was save to [Draft] folder.
5. Send the message.

(2) Zip all attachment files in one file and send.

– Steps
1. Gather all files in one Zip folder to attach to the message.
Example: Create the folder name “Data” and move all files (AAAAAAAAAA.txt, BBBBBB0123.xlsx, and BBBBBB0124.docx) to this “Data” folder.
2. Select 3 files (AAAAAAAAAA.txt, BBBBBB0123.xlsx, BBBBBB0124.docx) in “Data” folder.
* Select multiple files to attach by [Ctrl+Left Click].
Click [Ctrl+Left Click] on the file of AAAAAAAAAA.txt, BBBBBB0123.xlsx, and BBBBBB0124.docx to select 3 files at once.
3. [Right click] when the multiple files are selected and click [Send to]-[Compressed (zipped) folder].
4. Zip file is created in the folder, so re-name the file name if necessary.
5. Attached the zip file and send the message.

(3) Uninstall KB3055041

– Steps
1. Close Outlook 2010.
2. Click [Start]-[Control Panel] to open Control Panel.
When [View by:] is “Category” click [Uninstall a program].
When [View by:] is “Large icon” or “Small icon”, click [Programs and Features].
3. Click [View installed updates] on the left pane.
4. Select ”Update for Microsoft Outlook 2010 (KB3055041) XX-Bit Edition” on the list and click [Uninstall].
* The same name KB3055041 Update are listed, please uninstall both of them.
When first update is uninstalled, the message with re-start computer will be pop up, but click [Cancel] and continue to uninstall other KB3055041 update
5. Restart your computer after 2 updates of KB3055041 are uninstalled.
6. Start Outlook and check Outlook version from the following.
Click [File] tab-[Help]-[Additional Version and Copyright Information].
Confirm the number is below 7155 on “14.0.7155.5000”

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