Question 1

How do I send an email using gen_smtp client in Erlang?

Accepted Answer

Use gen_smtp_client:send/2 or send/3 with options like relay, username, and password. For example, as shown in the README, you can enable TLS with {tls, always} and specify authentication methods.

Question 2

gen_smtp vs other Erlang email libraries like gen_smtp alternatives?

Accepted Answer

gen_smtp is a pure Erlang library offering both SMTP client and server capabilities with OTP-style extensibility, unlike wrappers around external tools. It's best for integrated email handling within Erlang applications, whereas alternatives might focus only on client-side or lack server features.

Question 3

Does gen_smtp support IMAP for reading emails?

Accepted Answer

No, gen_smtp explicitly avoids POP/IMAP complexity and focuses on SMTP and LMTP for sending and receiving emails via servers. For IMAP support, you would need to use additional libraries or services.

Question 4

How to set up DKIM signing with gen_smtp?

Accepted Answer

Generate RSA or Ed25519 keys using OpenSSL, configure DKIM options (like s, d, and private_key), and use mimemail:encode with the dkim option as detailed in the README. Ensure your DNS records are updated with the public key.

Question 5

What are the dependencies for running gen_smtp?

Accepted Answer

gen_smtp depends on Ranch for socket acceptance and requires an eiconv module (e.g., from Zotonic/eiconv) for text encoding. You must add eiconv to your rebar.config and ensure Erlang/OTP compatibility, especially for Ed25519 support.

Question 6

Is gen_smtp suitable for high-volume production email handling?

Accepted Answer

Yes, it's production-tested in services like Gmailbox and hookup.email, with the README citing it handles over 100,000 emails without issues. Its robustness comes from the Erlang VM's concurrency and the library's memory management.

gen_smtp

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