Delta Chat

Every new messenger means another account, another contact list, and a reach limited to whoever installed it. Signal is excellent, but your mother has not installed Signal.

Delta Chat's idea is clever: use a network everyone already has — email.

Sign in with an existing account (Gmail, Outlook, a work address, your own server), the interface looks like an ordinary messenger, and messages are actually sent and received as mail. That yields properties no other app has:

• No new account. Your email address is your identity, and no phone number is involved.
• You can message people who do not have it. Your message arrives in their normal inbox as an email, and their reply comes back. Once they install Delta Chat the thread automatically becomes a chat and starts encrypting. This solves the cold-start problem that kills most new messengers.
• Decentralized. No single company owns the network. Change or lose your mail provider and you continue with another; your contacts are unchanged.
• Automatic end-to-end encryption. When both sides use Delta Chat, keys are negotiated automatically under the Autocrypt standard, requiring no understanding of PGP.

It is no longer text-only either: images, voice messages, video, file transfer, group chats, emoji reactions, message deletion, and WebXDC mini-apps that run a shared checklist, poll or small game inside a conversation.

To be clear about:

• Metadata protection trails purpose-built messengers. Email protocols mean servers know who wrote to whom, when and how large the message was. The content is encrypted; the fact of the contact is not. For metadata protection, use SimpleX or Signal.
• Messages to non-users are plaintext. If the recipient has no Delta Chat, your message is an ordinary unencrypted email. The interface labels encryption status clearly — read it.
• Speed depends on the mail provider. Email is less immediate than a chat protocol, and slow push on some providers delays messages by seconds to tens of seconds.
• Some mailboxes need configuration. Providers like Gmail may require an app-specific password or OAuth, documented officially. Self-hosted mail or IMAP-friendly providers work best.
• Group chat is constrained by the email model and large groups feel worse than in a dedicated messenger.

Who it suits: people who want encrypted messaging without asking family and friends to install anything, those who value decentralization and censorship resistance, and anyone already running their own mail server.