Safari losing encryption

When I check my gmail account, whenever I open an email with third-party links then I lose the "https://" in the url bar.

Same thing happens when checking my icloud email on icloud.com. Is that a bug in Safari? Does that mean that my icloud.com session is compromised afterwards as it has lost https encryption ? Or is this a "cosmetic" issue?

I can't imagine that Apple would have overlooked this and that most icloud.com sessions would lose encryption.

Thanks.