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What exactly is the file size limit of MSG files in New Outlook

sysadmin 140 Reputation points
2026-05-20T00:27:20.04+00:00

When I try to open an MSG with large file attachments for example, I get a message "Sorry, the file "email.msg" couldn't be opened. The file exceeds the maximum file size supported."

So, what IS the maximum file size supported?

I would prefer the answer in a whole number of bytes.

Outlook | Windows | New Outlook for Windows | For business
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Hornblower409 10,250 Reputation points
2026-05-20T05:40:25.9266667+00:00

https://learn.microsoft.com/en-us/answers/questions/5841684/how-to-open-previously-saved-emails

New Outlook can open .eml / .msg / .oft, but .msg and .oft have a 14 MB size limit. If your saved “Outlook item” is larger than 14 MB, it may fail to open in new Outlook

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  1. Shikha Ghildiyal 7,255 Reputation points Microsoft Employee Moderator
    2026-05-20T00:33:38.3166667+00:00

    Hi sysadmin,

    Thank you reaching out to Microsoft QnA.

    This problem occurs for one of the following reasons, depending on the kind of email account that you are using.

    Internet email account (POP3, IMAP, HTTP)

    You receive this error message because Outlook 2013 and later versions have a default attachment size limit of 20 megabytes (20480 KB) for Internet email accounts. This limit prevents your computer from continually trying to upload very large attachments that exceed the limits of most Internet service providers. This limit applies whether you are adding one large attachment that is greater than 20 megabytes (MB) or several attachments whose sum total size is greater than 20 MB.

    Microsoft Exchange Server email account

    If you are using an Exchange Server mailbox, you receive this error message (by default) if you attach one or more items to a message, and if the sum total of the attachments is greater than 10 MB (10240 KB). This attachment limit is not related to the limit in Outlook for Internet email accounts. This limit for an Exchange mailbox stems from the Maximum send size setting that is configured in the Transport Settings Properties dialog box by the Exchange administrator (Refer the following screenshot).

    Screenshot of the Transport Settings Properties dialog box.

    The steps to modify the default attachment limit depend on the type of email account that you are using with Outlook.

    If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.

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