Java: How to Attach Multiple Files in Mailgun Emails?

How can Java send an email with several attachments using Mailgun? Review the code snippet below:

public static JsonNode dispatchMailWithFiles() throws Exception {
    HttpResponse<JsonNode> reply = Unirest.post("https://api.mailgun.net/v3/" + SERVER_DOMAIN + "/messages")
        .basicAuth("api", MAILGUN_KEY)
        .queryString("from", "Notifier <[email protected]>")
        .queryString("to", "[email protected]")
        .queryString("subject", "Attachment Test")
        .queryString("text", "Checking file attachments via Mailgun.")
        .field("attachment", new File("/data/report1.pdf"))
        .field("attachment", new File("/data/image1.png"))
        .asJson();
    return reply.getBody();
}

In my experience working with Mailgun and Java, the key to successfully attaching multiple files lies in understanding how the client library handles repeated fields. Rather than assuming that sequential calls to .field with the same parameter name will automatically stack the files, sometimes it may require using a different method such as specifying an array or different keys if the library doesn’t support duplicate keys. I found that verifying the output of the HTTP request with a tool like Postman helps in debugging. Exploring Mailgun’s API documentation on attachments further clarified the expected format for files. Experimenting with sending one file at a time can guide you toward a better integration strategy when working with multiple file attachments.

In my experience using Mailgun’s Java API, sending multiple attachments reliably may require verifying the behavior of the HTTP client library. While your approach with repeated .field calls often works, I encountered cases where the library or API version expected added clarification in the multipart request. Performing tests with minimal files and monitoring the requests using a network inspector helped me ensure that all attachments were correctly passed. Always consult the latest Mailgun documentation and consider using dedicated multipart support if any inconsistencies emerge.

hey i’ve used attatchmnt with mailgun and it worked. i ended up calling .field(‘attachment’, file) for each, and sometimes updating the client lib helped. you might wanna check file paths too if you run into any hiccups.

During a recent project, I dealt with multiple attachment issues while using Mailgun with Java and found that ensuring each file was correctly processed required a bit of extra care. I noticed that sometimes the HTTP client library might not handle repeated fields as expected. In my case, verifying the actual HTTP request payload with a network monitor helped pinpoint order or naming issues. Upgrading to a version of the client library that offered better multipart handling proved effective. It can also be worthwhile to examine the precise multipart boundaries to confirm the server receives all files properly.

I faced similar challenges and eventually solved them by paying closer attention to how each attachment was added. I discovered that verifying file existence and correctly naming the parts in the request ensured that each was processed independently by Mailgun. Implementing thorough logging and comparing the constructed HTTP request with test cases made a big difference. Adjusting the code to set explicit file names for every part helped avoid any potential overwrites or misinterpretations by the API. This approach provided a stable resolution for sending multiple attachments reliably.