Outlook & Roundcube not showing paperclip icon for emails with attachments

When accessing cPanel IMAP email accounts in Outlook & Roundcube, for email sent from Apple Mail (Desktop and iOs) the paperclip icon which identifies emails with attachments does not display. After opening the email, the attachments are there and display/download OK. This appears to only apply to email which is sent from Apple Mail. On email I've sent from Roundcube, Outlook and Yahoo this issue doesn't occur.