I did speak to Domainfactory. They pointed out it must be a local Apple Mail problem, as they deliver the email to Microsoft Exchange, which sends it on to my Mac – and to my Iphone. An email which I have then opened, read and saved locally in Apple Mail, may then have lost its content when I look it up later, whereas other saved emails from the same person and near in time, may have kept their content. I estimate that the content-less emails make up about 25 % of locally saved emails on the Mac. Meanwhile, on Microsoft Outlook webmail the email will be available – with content. And also on my Iphone. The disappeared-content emails only happen on the mac. I have used Domainfactory for email and web for 20 years (as well as MacOS and Apple Mail locally) and before they migrated their email to Microsoft Exchange this problem has never occurred. Somewhere locally this disappearance is triggered – by some signal from Microsoft Exchange?