How to change the attachment size limitation in Outlook?

Author Kelly Last modified 2025-04-07

Sometimes, I can’t insert a big attachment successfully in Outlook, but get a warning dialog box saying the attachment size exceeds the allowable limit. See following screenshots. This error happens due to exceeding the size limitation of attachments in Outlook. In this article, I will guide you to change the attachment size limitation in Microsoft Outlook.

Change attachment limited size with Registry Editor (6 steps)

Change attachemnt limited size with Kutools for Outlook (3 steps)

Change attachment limited size with Registry Editor (6 steps)

To change the attachment size limitation in Microsoft Outlook, you have to modify the parameter of "MaximumAttachmentSize" in the "Registry Editor". And you can do it with following steps.

Step 1: Press the "Win" + "R" to open the Run dialog box, enter the "regedit" in the "Open" box, and click the "OK" button.

steps of changing attachment limited size with Registry Editor

Step 2: In the coming "User Account Control" dialog box, click the "Yes" button.

Step 3: Now the "Registry Editor" window opens. Open the "Preferences" folder via one of the following paths:

Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Preferences
Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Preferences
Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\Preferences
Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\Preferences

Step 4: Click the "Edit" > "New" > "DWORD (32-bit) Value", and name the new "DWORD" as "MaximumAttachmentSize".

Step 5: Double click the new "DWORD" to open the "Edit DWORD (32-bit) Value" dialog box, check the "Decimal" option, enter the attachment size limitation in the "Value data" box, and click the "OK" button. See screenshot below:

For example, you want to change the attachment size limitation to 100MB, enter "102400" in the "Value data" box.

Note: If you want to remove the attachment size limits in Outlook, just enter "0" in the "Value data" box.

Step 6: Close the "Registry Editor" window, and restart Microsoft Outlook.

After changing the attachment size limitation in the Registry Editor window, attachments will be inserted successfully only if their sizes are less than attachment size limitation. See the following screenshot:

Change attachemnt limited size with Kutools for Outlook

With above method to increase attachment size is a little complex, but if you have "Kutools for Outlook" -- a handy Outlook add-in, you can change the attachment limited size as you need in few clicks.

👉 Kutools for Outlook has a free version now, whose 70+ features are free for a lifetime. Download the Free Version Now.

Free install Kutools for Outlook, and then do as below steps:

1. Enable Outlook and click "Kutools" > "Options". See screenshot:
doc increase attachment size 4

2. In the "Options" dialog, click "Other" tab, and enter the limited size you want to change to into the textbox besides "Maximum Attachment Size" section. For instance, here I change the attachment size to 10MB (10240KB). See screenshot:
doc increase attachment size 5