Imagus - The extension is intended to complement image features that (I think) is missing from Opera by...
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
Image Max URL - Help find larger or original versions of images, including a customizable image popup feature
Tutanota - Get your encrypted mailbox for free.
Thumbnail Zoom Plus - The official site of the Thumbnail Zoom Plus add-on for Firefox
Mailvelope - Mailvelope open source project. OpenPGP in your browser.