When comparing mail.com vs Posteo, the Slant community recommends Posteo for most people. In the question“What are the best online webmail services?” Posteo is ranked 4th while mail.com is ranked 10th.
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Pros
Pro Unlimited storage
Pro Has over 200 domains to choose from
Pro Has native mobile apps and browser extensions
Mail.com has native apps for Android and iOS and browser extensions for Chrome, Firefox and Internet Explorer.
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.
Cons
Con Free plan is limited
Free plan lacks pop3 and imap access, phone support and includes ads.