(Stolen from https://faq.oit.gatech.edu/content/how-do-i-forward-email-attachment-office-365-outlook-web-app)
Unfortunately there is no built in way to just forward an email in Outlook 365. However, there is a workaround:
- Start a new email message
- Click the open separate window icon,
, located at the top right corner of the message window. This will open this message as its own window within your browser. - Next, organize your browser windows so that you can view both your mail folder listing and this message window.
- Drag the email, from your mail folder list, that you want to include in the message you are composing. It will be included as an attachment.
- Enter any other information and click Send button.
Note: The recipient(s) will receive this message which will include the message you dragged into it as an attachment.