Overview: In this article, you will firstly know what is the exact Outlook attachment size limit, Outlook restrictions, and effective techniques to increase limits in Outlook Desktop, Microsoft 365 and OWA. You will get to know about our professional solution to deal with large email attachments without affecting the performance of your mailbox.

Table of Contents

Know Outlook Maximum Attachment Size Limit

The size limit is set according to your Outlook version and email provider you use.

  • Most internet accounts have Outlook maximum attachment size limit of 20 MB
  • Whereas, in Microsoft Outlook 365 or Exchange Online, it can be as low as 10 MB to 25 MB
  • Talking about OWA (Outlook Web App), it totally depends upon Exchange server settings
  • So many users include not only the file, but the email text itself
  • If you are an Outlook user, then it will integrate with OneDrive to share secure links for files up to 250 GB
  • So, anything larger than this will be natively sharing files in Outlook

If you are an active Outlook user, then you might face an Outlook error your organization’s policies are preventing.

Why are there Restrictions in Outlook Attachment Size Limit?

There are various factors and security aspects which Microsoft took into consideration for Outlook size limits.

  • Microsoft put limits on attachment sizes in order to keep email services quick and efficient
  • Large files require more storage and bandwidth which leads to slow email sending
  • This will quickly fill up mailbox storage and have a high risk of upload or downloading problems
  • Having these limits enables organizations to keep email communication smooth and stable for all users
  • Loading constant big Outlook emails can lead to file corruption

 Errors Users Face While Loading Outlook Attachments

These are some of the errors which Outlook users deal with in regular basics.

  • Outlook attachment exceeds allowable limit
  • The file bigger than server allows
  • Attachment maximum size limit error
  • Message size exceeds fixed limit

The messages will show that either Outlook or the mail server has rejected the attachment.

Ways to Check Current Outlook Email Attachment Size Limit

For Outlook Desktop:

  • You need to create a new email
  • There, attach a large file
  • See if Outlook opens with a pop-up message or not

    For Exchange Admin Center:

Administrators can check transfer limits which is configured for:

  • Send connectors
  • Receive connectors
  • Mailboxes
  • Organization-wide settings

For Outlook Web App:

In Exchange Online or Exchange Server, your attachment policies typically limit OWA users by default.

Use Professional Solution to Manage Large Outlook Attachments 

Usually, users go with above manual methods to increase their size limit, but it is done on a temporary basis. After some time, you face the same problem again and it’s not that effective. So, you can go with our SysTools Outlook Attachment Extractor Software. You can easily extract and save bulk PST attachments to your desired location and no need to worry about Outlook attachment size limit. The tool can download attachments with the same folder structure, and it is completely offline and you don’t need to have Outlook installed.

How to Increase Outlook Attachment Size Limit Manually? 5 Methods

From this section, we will be focusing on different steps to increase attachment size in New Outlook.

#1. Use Registry Editor to Add Attachments File Size

Follow these steps to quickly increase Outlook attachment size limit.

  1. Firstly, press Windows + R, & type regedit and hit Enter
  2. Access the Outlook Preferences registry path according to your version of Outlook
  3. On the right pane, perform a right click on empty and select New > DWORD (32-bit) Value
  4. Name the new value MaximumAttachmentSize
  5. Double-click MaximumAttachmentSize to edit it
  6. Now, choose the Decimal option
  7. Fill the desired size of attachment in KB
  8. Press OK, quit Registry Editor, and restart Outlook

Note: Common values are:

  • 25600 = 25 MB
  • 51200 = 50 MB
  • 102400 = 100 MB
  • 0 Means = No Outlook limitation on the client-side, but may not be on the server end.

#2. Compress Large Attachments to Reduce File Size

If you reduce the file size, then in a way you can avoid Outlook limits completely.

  • Start by selecting the file
  • Right-click on it
  • Choose the option:

Send To > Compressed (ZIP) Folder

  • Get a ZIP file, which is attached to your outlook.

Users can best use it for:

  • Documents
  • PDFs
  • Excel Spreadsheets
  • Presentations

Drawbacks:

At this point large videos and high resolution media may still exceed Outlook limits.

#3. Change Outlook Attachment Size Limit Through Cloud Storage Links

You just have to load your attachments in any cloud platforms. So, you can share your files easily through a link.

Those are yours:

  1. Microsoft OneDrive
  2. SharePoint
  3. Google Drive
  • Go to any of these, and upload the file
  • Generate a sharing link from there
  • Add the link to the email

Benefits:

  • No restrictions in attachment file size
  • Have a faster email delivery
  • Easy collaboration

#4. Increase Attachment Size in Exchange Online 

You can change the message size limits in Exchange Online, if you are an administrator.

  1. Go to Exchange Admin Center and open
  2. Go to:

Recipients > Mailboxes

  1. Select the mailbox
  2. Edit Message Size Restrictions settings

You can Increase your:

  • Maximum send size
  • Maximum receive size

Note:

  • It may take some time to change across the environment.

#5. Increase Outlook Web App Attachment Size Limit

Follow these steps to extend the attachment limits. As, this is in control of Exchange policies.

  1. Firstly, launch Exchange Management Shell as an Administrator
  2. Type Set-TransportConfig command and increase the message size limit
  3. You can increase Send and Receive Size limit on a Mailbox using the Set-Mailbox Command
  4. Now, save the changes and allow Exchange to apply the new settings
  5. To verify that the new limit is applied, you can send a larger attachment via Outlook Web App

Drawbacks of Sending Large Outlook Attachments 

Users want to increase limits, but do not understand long-term damage. It can:

  • Increase the PST File Size
  • Slow Outlook performance
  • Having sync issues
  • Take lots of mailbox storage
  • Make your backup & migration process difficult

You need to take care of file size limits, as this is equally important as your attachments.

Best Practices:

These tips can help you avoid Outlook attachment size limit problem.

  • Always compress files whenever possible
  • Send out links in place of big attachments
  • Delete unknown emails present in Outlook mailboxes
  • Regularly archive old emails
  • Try to store some large files in specific locations, rather than keeping everything within Outlook

Final Note

There is an Outlook attachment size limit option to make sure your email delivery, server performance, and to manage the mailbox section. We have described available methods like using Outlook desktop, Microsoft 365, cloud platforms, and Outlook web app. All these steps have some kind of limitations , so it’s better to use our automated solution tool to manage your Outlook attachments.