Not as safe as an open-source client, like Thunderbird or SeaMonkey’s mail. Vivaldi has been hesitant to release their source code, and they actually released a page full of excuses about why they shouldn’t need to.
Edit: you changed the title/text, so my answer is… Thunderbird is the most private email client. Originally, this post was about Vivaldi
Not as safe as an open-source client, like Thunderbird or SeaMonkey’s mail. Vivaldi has been hesitant to release their source code, and they actually released a page full of excuses about why they shouldn’t need to.
Edit: you changed the title/text, so my answer is… Thunderbird is the most private email client. Originally, this post was about Vivaldi