1. Check to make sure you are using the correct email address
2. Make sure your Outlook version is compatible with attachment expectations
3. Check filters to make sure your emails are not being diverted to spam or junk folders
4. If the attachment is larger than 20 MB, use Outlook’s OneDrive integration for attachment delivery
5. Installing the latest version of Outlook may also help with sending and receiving attachments
6. Make sure that you give the recipient permission to open the attachment