Generally, we do not pay attention to the attachment file size when sending emails using Microsoft Outlook. However, the files we attach have to be under the limit specified for Outlook, which is 20 MB. Whenever your email attachment size bypasses this limit, Outlook will generate an error and prevent you from attaching the file or sending the email.
The attachment size exceeds the allowable limit
Related Article: Sending or receiving reported error (0x80042109) in Outlook
If you’re an Outlook user who has to regularly send large files as email attachments, you can change Outlook’s default attachment size limit. However, there is no direct setting to change this in Outlook. Instead, you’ll need to use a simple registry tweak to set your desired limit for email attachment size.
- Press Windows Key + R combination, type put regedit in the Run dialog box, and hit Enter to open the Registry Editor.
In this registry location’s right pane, do a right-click in the empty space and choose “New -> DWORD Value.”
Name the newly created DWORD as Maximum Attachment Size. Double click on this REG_DWORD to modify its Value data.
In the above-shown box, set the Value data to 0 to allow an unlimited attachment size. If you want to extend the limit, for example, to 50 MB, then put 50000. Click OK, and close the Registry Editor.
Reboot the machine to make changes effective.