Sometimes you receive some emails which are mostly (and correctly) categorized as spam email by your email provider and you are almost sure that they are in fact spams. However, you are curious to open and take a look at the contents of some of them to see what they have. I was wondering is there any risk involved at receiving/opening such emails, of course without clicking on any of its links or downloading its attachments? Is it recommended to not even open them at any case?
Further, It would be great if you could consider and compare in your answer the cases of using an established email provider (e.g. Gmail, Yahoo, Live, etc.) vs. the ordinary (self-hosted) email systems, as well as the difference (if any) in this regard between using internet browsers for viewing email vs. using email software clients (e.g. Mozilla Thunderbird, Microsoft Mail, etc.) or mobile email apps.