Missing attachments in Microsoft Outlook

Updated: 11/13/2018 by Computer Hope
Microsoft Outlook logo

This page contains information about why an attachment is missing or not sending through Microsoft Outlook and Microsoft Outlook Express. These are two separate programs, make sure you follow the suggestions for the version of Outlook you're running.


If you need help sending attachments, see: How to send an attachment or photo through e-mail. If you're using an e-mail client that is not Outlook, and cannot receive e-mail, see: Why can't I receive any e-mail attachments?

Attachment is too big

If the file attachment is too big (over 20 MB), the file may be stripped (excluded) from the e-mail because of the policies of your ISP. Also, Outlook may have a size restriction on the size of attachments. Check with your ISP or network administrator for more information about e-mail restrictions. In general, if the attachment is bigger than 20 MB, we suggest using a file sharing service rather than e-mail.


The latest versions of Outlook support a file attachment up to 20 MB.

Problems with Outlook authentication

If there are problems with how Outlook authenticating you account, it can cause problems without sending attachments. Often, these problems can be resolved by logging out, then logging back into Outlook. Follow these steps to log out and log back into your account.

  1. Close all Microsoft Word, Microsoft Excel, or Microsoft Outlook open windows.
  2. Open only Microsoft Outlook.
  3. Click File, Office Account, and then Sign Out.
  4. Click Yes to sign out and then close Microsoft Outlook.
  5. Re-open Microsoft Outlook and sign back into your local or Microsoft account.

Antivirus protection blocking attachment

If you have an antivirus protection program installed on your computer, and are having problems opening or viewing attachments, try temporarily disabling your antivirus software. (After checking if that was the problem, don't forget to re-enable it!)

Disable Microsoft Outlook Add-ins

Microsoft Outlook add-ins can cause problems with attachments. Disable all add-ins by following these steps.

  1. Open Microsoft Outlook.
  2. Click File, Options, and then Add-ins
  3. Under Manage click COM Add-ins.
  4. Click the GO button next to Manage and then uncheck all the Add-ins.

Microsoft Outlook Add-ins

  1. Once everything is disabled, click Ok.
  2. Close Microsoft Outlook and then re-open Outlook to see if the attachment issue is resolved.

Microsoft Outlook 2000 is set up to accept certain sized files

Microsoft Outlook 2000 and earlier can be set up to only accept files of a certain size. If you're attempting to receive a large file, verify this feature has not been enabled by following these steps.

  1. Open Outlook.
  2. Click Tools.
  3. Click Options.
  4. Click the Mail Delivery tab.
  5. Under Mail Delivery, make sure the box "Don't download messages larger than xxx KB" is not checked.

ISP or e-mail provider is removing the attachment

In some cases, the ISP or e-mail provider scans incoming e-mails and attachments, and automatically delete e-mail if it considers an attachment unsafe. Your ISP may also fail to deliver your e-mail if you exceed a disk space or bandwidth quota. Check with your ISP to make sure your e-mail is not being deleted because of data restrictions on your service account.

To determine if this is causing your issue, you would need to contact either your Internet service provider or e-mail provider. An alternative solution to this recommendation is to set up a free webmail account and try receiving the attachment through the webmail address.

Microsoft Outlook Express is blocking the attachment

Microsoft Outlook Express is set up by default to block some attachments, for example, .exe files and other executable files Microsoft considers unsafe. Although this feature can be disabled, we suggest you leave it enabled if you're running Outlook Express. If you want to send an executable file through e-mail, compress the file.

For users who are aware of the potential risks of accepting executable files and want to disable this feature, follow these steps.

  1. Open Outlook Express.
  2. Click Tools.
  3. Click Options.
  4. Click the Security tab.
  5. In the Security window under Virus Protection, uncheck "Do not allow attachments to be saved or opened that could potentially be a virus."
  6. Click OK.

Below is a listing of file extension Microsoft considers unsafe when sent through e-mail.

.ad, .adp, .crt, .ins, .mdb, .mde, .msc, .msp, .sct, .shb, .vb, .wsc, .wsf, .cpl, .shs, .vsd, .vst, .vss, .vsw, .asp, .bas, .bat, .chm, .cmd, .com, .exe, .hlp, .hta, .inf, .isp, .js, .jse, .lnk, .msi, .mst, .pcd, .pif, .reg, .scr, .url, .vbe, .vbs, .ws, and .wsh.

For additional information about each of the above file extensions, see our file extensions page.