will not display message if there is an attachment also [v60.8.0 (mac)]
Not all attachments cause this but most seem to.
Additional System Details
- User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:67.0) Gecko/20100101 Firefox/67.0
Is the attachment visible when you access the account through webmail? Is there an antivirus program on your system scanning email?