Check the IT policies of your Exchange email server to see if there are any restrictions on types of files allowed as attachments. If configured, consider using secure file-sharing services that provide managed access to attachments.

1. Verify any file extensions restrictions on email attachments.
2. Check the file size of the attachment and determine if it is too large to be sent.
3. Ensure the file is not in a prohibited or restricted format.
4. Utilize secure file-sharing services that provide managed access to attachments.