Attachment size limitations

Outlook does not impose any size limit on attachments. However, most e-mail server administrators and Internet service providers (ISPs) do set limits on the overall message size, which is the sum of all attachments plus the content of the message itself. Typically, premium-level services provide more e-mail file storage space and allow larger messages than standard-level services. For more information on the maximum allowed message size, contact your ISP or the e-mail server administrator in your organization.

If you are attaching a very large file, you should first compress the file by using a zip program. Outlook files that are saved in the default Open XML Formats with the following file extensions are automatically zipped: .docx, .dotx, .xlsx, .xltx, .pptx, .potx, and .ppsx.

Problems with .zip files

If files that you attach are zipped when you do not expect them to be, check to see whether a zip utility has been installed in Outlook as a COM add-in. You can disable this sort of add-in by doing the following:

1. On the Tools menu, click Trust Center, and then click Add-ins.
2. In the Manage list, click COM Add-Ins, and then click Go.
3. In the COM Add-ins dialog box, clear the check box next to the add-in name, and then click OK.

Attach an item to a message

You can attach items (item: An item is the basic element that holds information in Outlook (similar to a file in other programs). Items include e-mail messages, appointments, contacts, tasks, journal entries, notes, posted items, and documents.) and other messages to a new message:

1. On the File menu, click New, and then click Mail Message.
2. On the Message tab, in the Include group, click Attach Item

3. In the Look in list, click the folder that contains the item that you want to attach.

4. Click the item that you want, and then click OK.

You can also attach an item from the new message's Insert tab.