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Microsoft Outlook tries to protect users from malicious attachments by blocking them. What if you're sending something that's legitimate, but blocked?

How can I send someone an attachment, if it's blocked by their copy of Outlook?

Sending and receiving attachments appears to be risky business these days. The recent MyDoom virus was mostly an attachment-borne virus and it's still causing a fair amount of trouble. Unfortunately that trouble just proves the point that a lot of people still cannot be trusted to know the difference between a safe attachment and a malicious one.

To make attachment borne viruses more difficult to propagate Outlook and Outlook Express now come configured by default to prevent access to certain types of files because they are common targets of viruses. Unfortunately, the ability to transfer files as attachments via email has become a critical component of many people's use of the internet. If your recipient can't open your document then what can you do?

I'm going to assume that asking your recipient to work around the issue at their end is not an option. (It's outlined in this previous article: Why can't I open attachments in Outlook? Instead we're going to look at things you can do.

The simplest and most over looked option is simple: Does it have to be sent as an attached document at all? I've often received attached documents that are nothing more than lightly formatted text. It could just as easily have been sent as the body of the email message itself. Not only does this completely bypass Outlooks attachment filter but it makes for smaller email that is quickly sent and received.

Do you have the ability to send it in another format? If the document is only for the other person to read perhaps you can save it as a PDF which will preserve all of the graphics and formatting and is typically not blocked by default. If you don't already have the ability there are several Adobe PDF creation tools on the market such as Adobe Acrobat as well as others, some of which are free. In some cases even sending as a plain text file is sufficient though if that's the case I'd once again question whether it should be sent as an attachment at all.

Just ZIP it. The ZIP file format is a compressed archive. It's a way to compress and combine several files into a single file from which they can be later extracted. Windows XP actually has some rudimentary support for ZIP files built in so it's very likely that if you send your attachment as a ZIP file then your recipient will be able to access it. The popular ZIP programs include WinZip and PKZip.

Rename it. Outlook bases its decision on whether or not to block a file by looking at the file's extension (the characters after the last '.' in the file name). If you rename FOO.DOC to FOO.LEO then email it as an attachment then your recipient should be able to save FOO.LEO to disk, rename it to FOO.DOC, and be on their way.

Don't use email. It might just be that email is simply the wrong solution to transfer the file. The most common alternative if you have the ability is to upload the file to a web site and then send a link to the file rather than the file itself. Your recipient can then simply download the file at their convenience. Sending large attachments or sending attachments to a large number of people is considered bad "netiquette" anyway because of the resources and bandwidth used. This approach allows people to get their email quickly and then gives them a choice to download the file now or later or not at all.

Now it kind of goes without saying but I'll say it anyway - all of the techniques I've listed above are ways to circumvent Outlooks attempts to keep the recipient safe from viruses. If your document contains a virus then ZIPping it, renaming it, or uploading it won't make the virus go away when that document finally lands on your recipient's computer. This then implies that you as the sender have a responsibility to ensure that the documents you're sending are in fact virus free.

Article C1895 - February 17, 2004 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

July 16, 2004 9:06 PM

A good way to send documents that are rejected by email is to use a free service such as or

September 1, 2004 10:05 AM

I applied to a job listing on Monster using attachments, which was the prefered way. I got an email back asking me to resend in word format. I have Windows XP does this have anything to do with them not being able to open the file? I don't understand what they want me to do. I have this on a disk and also saved to my documents. Any suggestions?

September 1, 2004 7:41 PM

They're asking you to use Microsoft Word to create the document. Alternately you can use another word processor, and save the document in Microsoft Word format.

May 1, 2005 8:15 AM

Could you please tell me if there is any way that I can tell if someone has me blocked on their IM. If so could you please let me know.

May 1, 2005 8:56 PM

Not that I'm aware of.

August 4, 2005 5:55 AM

I learnt some very useful tips from this website, though I have a problem. I've been trying to send an email with a PDF file attached to it and I get a message that says that the message content is too large for the recipient. What does this mean and how can I solve this problem in order to send my email? I am using Microsoft Outlook and running Windows XP on my computer. Help!!!

August 4, 2005 1:22 PM

Many email servers will not accept email over a certain size. There's not neccessarily anything you can do about that if it's happening at your recipient's side. At best, you can attempt to make your document smaller, or get it to them some other way - perhaps transferring in an IM conversation, or uploading it to a web site that they can then download from.

August 17, 2005 6:14 PM

I've got this problem in reverse. OE displays'Removed access to the following unsafe attachment in your mail (followed by attachment name). I can't open ANY attacment to ANY Email. I'm running on WINXP(home)

November 15, 2005 3:27 PM

Oftentimes when I send an attachment with Outlook, the recipient says that they didn't receive it, even though my "sent" file shows that I did attach it. If I send them the same attachment in Outlook Express, everything is fine.

I know that Outlook automatically attaches its little .dat file which non-Outlook users see (and question). Does that have anything to do with it? I have not asked the "non-recipients" what email client they were using 'cuz I shouldn't have to.

I really like the calendar feature of Outlook, but otherwise find the rest of it frustrating compared to OE...



November 15, 2005 8:44 PM

Sounds like you're running an older version of Outlook if there are winmail.dat attachments. Also implies those emails are "Rich Text". I would use Plain Text formatting when sending the mail. (Or, perhaps HTML.)

November 16, 2005 6:07 AM

You're right; it's 2000. I think I'll go back to OE, it was easier. Thank you!

November 19, 2005 7:04 AM

Ok I am having a problem with a downloaded zip file. I can not get it to copy to a disk how do i do this I have tried to back it up and that did not work and I have tried 5 brand new disk but always come up with the same error message telling me that the disk I am using is no longer usable.. It is brand new a sony cd-r 700mb disk. is there something that I should do to the file before I save it to the disk Like unzip it or no.

February 21, 2006 5:29 AM

We solved the problem of sending large data files/folders using Foldermail:

Works in the background and is unaffected by intermittent connectivity!

Hope it helps,

March 6, 2007 4:24 AM

Oh My gosh. David I've started having the same problems today. I'm running outlook 2007 and two recipients did not get some attachments but they got of them is running outlook express. and Yes when I send them from OE they get them no worries. There has to be answer for this in the settings somewhere. Microsoft seriously need to look at improving their compalability and there service...

greg thomas
April 12, 2007 2:00 PM

I recently sent a internal office e-mail and it was a webpage link. When the recipient opened it They were showing attachments which were from his local computer. How is this possible. WE recently just updated to Microsoft exchange 2007?
Any ideas why this would happen?

sandeep singh
December 3, 2007 10:03 AM

when ever i am tring to attach any file to a mail, it not getting attached ,suggest what ot do

January 12, 2008 4:43 AM

One of my collegue send me a attachment to me and another person.I am not recived the attachment the other one received the attachement?he send the mail in to field only no cc or bcc.Can you please tell me why?

April 13, 2008 7:09 PM

I can't send attachments in Outlook, or Outlook Express. I can receive e-mails with Attachments fine, and I can send e-mails without Attachments fine. Please, help!

January 22, 2010 6:19 AM

If your attachment is being blocked by the recipient's email program I suggest that you send it via a file transfer service. The easiest one I've found to do this with is Tonsho.
With their system you send an email as normal, they automatically take out the attachment and put it on a secure website, the person you are sending it to gets a link from them including the message you wrote, they click on the link and download the file. This avoids the problem of their Outlook blocking the attachment. I started using a free account with Tonsho but they also offer premium accounts if you need them. Oh, and you can also just use them via the web as well.

February 25, 2010 8:41 AM

I am upset I can not send e mails I am blocked I am not sending spam .I am looking for work how can I ctop the block plzz help

If you're looking for work you should be using a service more reliable and with a more preofessional reputation than Hotmail.

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