When comparing Posteo vs Yahoo! Mail, the Slant community recommends Posteo for most people. In the question“What are the best online webmail services?” Posteo is ranked 4th while Yahoo! Mail is ranked 8th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Numerous feature/advantages
Pro No ads
Posteo is ad-free with no ads when using their email services.
Pro Support for IMAP/SMTP
Posteo supports email clients such as Thunderbird and Claws Mail which will allow for greater control over encryption and user's private keys.
Pro No Personal Information required to register
Registration through VPN is allowed and no personal information is required, just a username and password.
Pro Very secure
Posteo does very well on Dismail's server list and it supports end-to-end encryption with PGP. This can be done in the browser or with an email client, and Posteo has a help section on how to set up encryption.
Pro Inbound encryption
You can select an option to encrypt inbound email from their server with a user-provided GPG key.
Pro Encrypted storage
You can select an option to encrypt all of your emails stored on their servers.
Pro Tabs
With this Yahoo! Mail feature users can open any e-mail in a new tab and get back to the mail list without having to close the e-mail that the user is currently reading.
Pro Background wallpaper
Similar to Mail app bundled in Windows 10, Yahoo! Mail allows users to set images from Flickr as the background image for the app.
Pro Stationary
Stationary is an add-on that's only available in Yahoo! Mail. It allows users to customize and enhance the look of the email. Things like image borders, letter style etc. can be changed before sending the email to intended recipients.