The difference is signal has millions of users and most people have already maybe heard of it.

But it's a free Europe-based provider that's not US big tech. A better suggestion?

To be clear, I use a paid service (Mailbox.org) for my main email, as everyone should do.

Which applies to 99% of people making Delta Chat not a viable alternative to WhatsApp.

The Fediverse has the same problem that Linux, and Open Source in general, struggles with. The barriers to entry and network effects work against widespread adoption.

Until technology is packaged in a way that makes it dead simple and/or unavoidable, people won’t make the effort to move en masse.

Regarding SMTP:

SMTP (Simple Mail Transfer Protocol) is a foundational technology for email, but it has some limitations. Here are some ways it could be improved:

• Security: SMTP was designed in a time of less pervasive security threats. It lacks built-in encryption and authentication mechanisms, making it vulnerable to eavesdropping, spoofing, and spam. While extensions like TLS/SSL and authentication methods exist, they are not universally implemented or enforced.

• Efficiency: SMTP is a "chatty" protocol, meaning it involves multiple back-and-forth exchanges between the client and server. This can lead to latency and increased resource consumption, especially for large emails or bulk sending.
• Deliverability: SMTP doesn't have mechanisms to guarantee email delivery. Emails can get lost, delayed, or filtered as spam. While techniques like SPF, DKIM, and DMARC help, they are not foolproof.
• Features: SMTP is primarily designed for sending emails. It lacks features for managing email content, tracking delivery status, or handling complex email workflows. Possible Improvements:
• Mandatory Encryption: Enforcing TLS/SSL encryption for all SMTP connections would protect email content from interception.
• Stronger Authentication: Implementing more robust authentication mechanisms would prevent spoofing and ensure that emails originate from legitimate senders.
• Enhanced Deliverability: Developing mechanisms to track email delivery, provide feedback on delivery failures, and reduce spam filtering would improve deliverability.
• More Efficient Communication: Exploring alternative protocols or extensions that reduce the "chattiness" of SMTP could improve efficiency.
• Integration with other technologies: Integrating SMTP with other technologies like REST APIs or message queues could enable more complex email workflows and features.

It's important to note that some of these improvements are already being addressed through extensions and best practices. However, there is still room for improvement in making SMTP a more secure, efficient, and reliable technology.

~~That said, it looks like Delta Chat doesn't actually use SMTP, having scanned through the website. Though I'm honestly unsure either way as it was only a scan.~~

Never mind:

Delta Chat doesn't use its own proprietary protocol. Instead, it cleverly leverages the existing email infrastructure for message delivery. Here's how it works:

• Core Protocol: IMAP/SMTP - Delta Chat primarily uses the standard Internet Message Access Protocol (IMAP) for receiving messages and Simple Mail Transfer Protocol (SMTP) for sending them. These are the same protocols your regular email client uses.
• Encryption: Autocrypt & OpenPGP - To ensure secure and private communication, Delta Chat implements end-to-end encryption using the Autocrypt standard and the OpenPGP standard. This means your messages are encrypted in such a way that only the intended recipient can decrypt and read them.
• Secure Key Exchange: SecureJoin - Delta Chat also utilizes the SecureJoin protocol for secure key exchange. This helps to prevent man-in-the-middle attacks and ensures that only authorized parties can establish secure communication. In essence, Delta Chat works by:
• Sending encrypted messages as emails: When you send a message in Delta Chat, it's actually sent as an encrypted email to the recipient's email address.
• Receiving encrypted messages as emails: Delta Chat constantly checks your email inbox for new encrypted emails that are meant for you.

• Decrypting and displaying messages: When a new encrypted email arrives, Delta Chat decrypts it and displays it to you in the chat interface. This approach has several advantages:

• Decentralization: No central server is required to store your messages, making it more resistant to censorship and single points of failure.
• Openness: It leverages existing email infrastructure, making it interoperable with any email provider.
• Security: End-to-end encryption ensures that your messages remain private and secure.

If you're interested in learning more about the technical details, you can check out the cryptographic analysis of Delta Chat available on the Cryptology ePrint Archive: https://eprint.iacr.org/2024/918