Troubleshoot attachment problems in Outlook
support.microsoft.com › en-us › officeIn Outlook, select File > Options > Trust Center > Trust Center Settings >Attachment Handling > Turn off Attachment Preview. To turn off a specific attachment previewer, click Attachment and Document Previewers, clear the check box for a previewer you want to turn off, and then click OK. How do I open or preview PDF attachments?
Unable to attach files in Outlook.com
support.microsoft.com › en-us › officeIf you reply to a message that has an attachment, the attachment won’t be included in the reply. If you need to keep original attachments, Forward the email instead. You can only attach files to calendar events that you or a delegate created. The size limit for an email in Outlook.com is 29 MB. This includes all text, inserted and attached files.