Outlook blocks certain file types and has a file size limit of 25 Megabytes.
Blocked file types
View the Blocked attachments in Outlook page for a list of blocked file types and tips for saving files as acceptable file types.
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If you need to exchange a file type blocked by Outlook, use LiquidFiles.
File size restrictions
As a file is attached to a message, its size can inflate beyond the size of the attachment limit due to encoding. It is also possible that the receiving party, if outside of the Office 365 system, may have a lower message size limit that will not allow larger attachments to make it through.
If what you need to send appears to be too large, try zipping the file to compress its size or check out our selection of file sharing tools.