Windows 10: How to stop Win 10 with Outlook sending attachments as Winmail.dat Solved

  1.    30 Sep 2017 #1

    How to stop Win 10 with Outlook sending attachments as Winmail.dat

    I have just joined this forum. Am an XP user but have been asked by a friend to help set up e-mail on a Win 10 laptop running MS Outlook.
    Mostly it works fine but sometimes encodes attachments as Winmail.dat files which recipients can not open or use.
    This problem is widely reported on internet.
    I have tried every solution I have read, without success. These include ensuring that Outlook sends messages as HTML or Plain Text (NOT as Rich Text) and applying a change to the registry to inhibit poduction of Winmail.dat files. Yet still the problem persists.
    Sending to another Outlook address is OK. Sending to a GMail address works but sending to a BTInternet address never works in that all attachments (doc / docx / jpg etc.) get sent as Winmail.dat which I can not open. Moreover I use MS Outlook Express to access my e-mail accounts and this program fails even to recognise Winmail.dat!
    It seems as if certain ISPs interact with Outlook and cause it to send Winmail.dat attachments.

    Is anyone aware please of a hard and fast solution which guarantees that OUTLOOK will NEVER generate Winmail.dat attachments?

      My ComputerSystem Spec

  2. Posts : 8,889
    Windows 10 Pro x64 Build 1803
       30 Sep 2017 #2

    Hi CMOORE100.

    Welcome to the TenForums @CMOORE100

    Did you clear the auto complete cache after making the changes?

    File => Options => Mail => Sending Messages Section => Empty Auto Complete List (These are steps for 2013, your may be slightly different).

    Once clear try resending with Plain Text.

      My ComputerSystem Spec

  3.    02 Oct 2017 #3

    Many thanks for your very rapid and helpful reply. I am provisionally of the view that yur solution has solved my problem. However I would like to evaluate it a bit more and ensure that there are no bugs (none so far). I will then post a full reply describing all which I have done to overcome what seems to be a well known problem with WIN 10 / Outlook which MS appear to be aware of but have failed to address either by knowledge paper or, preferably, software update.
    Will post further in2 or 3 days, but am optimistic thanks to your input Ken.
    Very many thaks.
      My ComputerSystem Spec

  4. Posts : 8,889
    Windows 10 Pro x64 Build 1803
       02 Oct 2017 #4

    Great. The cache was remembering the old settings for contacts. By deleting, the new settings come into play. Glad the forum could help.

      My ComputerSystem Spec

  5.    03 Oct 2017 #5

    MS Outlook attachment problem with Winmail.dat issue

    WIN 10 (64 bit) with OUTLOOK 2016 send E-Mails which some recipients are unable to open or read.

    The problem most commonly encountered, to judge from many internet pleas for help, is that normal e-mail messages are sent and received satisfactorily but attachments – whatever their file extensions – are sometimes apparently not sent or not openable. There are also reports that some e-mail main texts are apparently not sent or not openable. This note is based specifically on WIN 10(64) plus OUTLOOK 2016, but my extensive reading for a solution has revealed that other WIN / OUTLOOK issue combinations also give rise to the same or similar problem. It may therefore well be possible that the following actions will also be of assistance with these.
    The root problem is that OUTLOOK sometimes encodes messages and/or attachments as WINMAIL.dat files and sends these. Many non-MS mail programs can not recognise and/or open these. WINMAIL.dat is a format used in times past for sending Rich Text Format (RTF) messages. I am uncertain why MS persists with this heritage I have found in limited testing that some ISPs seem to receive OUTLOOK attachments OK (because these are sent as their original files with “normal” extensions) whereas another ISP appears to prompt their conversion to WINMAIL.dat and then can not open them. I have, by the way, eliminated any possibility that the problem stems from my receiving computer. My accounts are of the “web based” type and I can open my E-mail boxes by web access direct to the ISP.
    My testing (not comprehensive) has shown that when OUTLOOK is used to send attachments to a account they are received OK but when the exact same attachments are sent to a they are received as WINMAIL.dat encoded files. It is thus doubly unsatisfactory in that one can not rely on the receipt of attachments sometimes, but not always.
    Here are the 3 steps I took :- 1.. Modify the registry to inhibit generation of Winmail.dat files. To do this a.. Open program REGEDIT (Windows key plus R) b.. Go to Computer/ HKEY_CURRENT_USER/ SOFTWARE/Microsoft/Office/16.0/Outlook/Preferences c.. Create a new DWORD(32bit) called Disable TNEF
    d.. Enter a value of 1 ie.0x00000001 (1) e.. Exit Regedit 2.. Set up OUTLOOK so as NOT to send messages in RTF format. a.. Open OUTLOOK b.. At top left SLCk the blue FILE tab. File page opens.
    c.. In list at LHS SLCk OPTIONS. d.. From OPTIONS find and SLCk MAIL. e.. In MAIL option scroll down to COMPOSE MESSAGES f.. Find CHANGE EDITING SETTINGS g.. Select PLAIN TEXT format option in box. (HTML option may also be OK but RICH TEXT FORMAT – RTF – must NOT be selected). h.. Close the MAIL options page(s).
    3.. Set up OUTLOOK not to auto-complete addressees and empty the auto complete cache. a.. Open OUTLOOK b.. At top left SLCk the blue FILE tab. File page opens. c.. In list at LHS SLCk OPTIONS. d.. From OPTIONS find and SLCk MAIL. e.. In MAIL option scroll down to COMPOSE MESSAGES
    f.. Select SEND MESSAGES section. g. UNCHECK box labelled “Use auto complete list to suggest names when typing To/cc/bcc lines”. h.. Find and SLCk the “Empty auto complete list” i.. SLCk YES in response to “ARE YOU SURE” pop-up box j.. There is no apparent response to step i. k.. Close OUTLOOK mail option page(s). l.. For good measure re-start the PC.

    Notes : i.. At step 3e with OUTLOOK 2013 scroll to SENDING MESSAGES section. ii.. In OUTLOOK 2003 and 2007 for procedure section 2 : iia.. Access OPTIONS from the tools menu iib.. Click MAIL FORMAT tab iic.. Click INTERNET FORMAT iid. Under Outlook Rich Text Options click either Convert to HTML format or Convert to Plain Text format. Get rid of any reference to RTF.
    iii. This note is written based on Win 10(64bit) plus Outlook 2016. Other OS/Outlook versions may vary in function and detail.
    iv.. Some versions of OUTLOOK provide for the message sending format to be varied between addressees in the address book. To check for this each address book entry needs to be examined from its PROPERTIES values. These should be opened and set to HTML or PLAIN TEXT and never RTF (or TNEF). v.. With my problem the solution was achieved after step 3. It appears that the auto-complete cache “remembers” previous settings and hence it needs to be deleted.
    vi.. Step 3 was the vital action and was kindly contributed by Caledon Ken at TEN FORUMS I will mark the thread as resolved after further evaluation, but am highly optimistic. .
      My ComputerSystem Spec


Related Threads
My wife's laptop on the same network as my PC and using the same version of Outlook 365 displays the paperclip indicating the message has an attached file. But when the message file is opened the attached file is no longer displayed (and available...
Hi, I'm running Outlook 2010 in an Exchange 2010 environment. We are having an issue with Outlook blocking attachments. It is NOT blocking them based on extension. I have found many articles about unblocking attachments by extension but this does...
To make more space on the C: drive, I moved onedrive folder to another another drive. Didn't realize that the pst file is residing under onedrive. I linked the outlook 2010 data file to the new location of pst file but cannot send or receive emails....
Hi, Upgraded both our Desktop & Laptop to Windows 10 in the past few months. Last week I tried to access some Outlook emails that were more than two years old, the attachments & emoticons do not appear. This is on both PC's & the same result...
Sending emails via Outlook in Browsers and Email
Outlook appeared at first to be working perfectly until I tried to send an email. It will not leave the outbox and I get the following message. Sending' reported error (0x800CCC13) : 'Cannot connect to the network. Verify your network connection or...
Our Sites
Site Links
About Us
Windows 10 Forums is an independent web site and has not been authorized, sponsored, or otherwise approved by Microsoft Corporation. "Windows 10" and related materials are trademarks of Microsoft Corp.

© Designer Media Ltd
All times are GMT -5. The time now is 19:48.
Find Us