Question 1

How to send an email with attachments using Simple Java Mail?

Accepted Answer

Use the EmailBuilder to create an Email object with the withAttachment method, specifying files or datasources, then pass it to a Mailer instance for sending. The README provides code examples showing the fluent API for adding multiple attachments easily.

Question 2

Simple Java Mail vs Apache Commons Email: which is better for Java projects?

Accepted Answer

Simple Java Mail offers a more modern API with better support for advanced features like DKIM, S/MIME, and Spring integration, while Apache Commons Email is lighter but less feature-rich. Choose Simple Java Mail for complex email workflows; Commons Email for simpler, legacy-compatible needs.

Question 3

How to configure DKIM signing in a Spring Boot application?

Accepted Answer

Add the DKIM module dependency, then configure properties like simplejavamail.dkim.signing.domain and private key in application.properties. The library's Spring support automatically applies these settings when building the Mailer, as detailed in the security documentation.

Question 4

Can Simple Java Mail read Outlook .msg files and convert them to EML?

Accepted Answer

Yes, the EmailConverter class provides methods like outlookMsgToEmail and emailToEML to parse Outlook .msg files and convert them to standard formats. This is useful for processing emails from Microsoft environments without Outlook installed.

Question 5

What are common errors when using the batch module for async sending?

Accepted Answer

Issues often arise from misconfigured connection pools or missing module dependencies, leading to exceptions like NullPointerException. Ensure the batch-module is on the classpath and review the cluster configuration settings in the documentation.

Question 6

How to handle S/MIME encryption without the optional module?

Accepted Answer

You cannot; S/MIME features require the smime-module dependency. If omitted, calling S/MIME methods will throw exceptions, so you must add the module explicitly for encryption or signing, as noted in the release notes about fail-fast behavior.

Simple Java Mail

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