I’m trying to figure out how to send emails through MailGun’s messaging API when I need to include file attachments that are in binary format. I’ve been working with their REST API endpoint but I’m not sure about the proper way to handle binary data attachments.
Has anyone successfully implemented this before? I’m looking for practical examples or code snippets that show how to properly format the request when dealing with binary files like PDFs, images, or documents. The main challenge I’m facing is understanding how to structure the multipart form data to include both the email content and the binary attachment data.
Any guidance on the correct headers, encoding methods, or request structure would be really helpful. Thanks!
been there! use multipart/form-data and attach the binary file straight to the ‘attachment’ field. don’t bother with base64 encoding - mailgun handles that automatically. just set your content-type header correctly and you’re set. works great with pdfs and images in my experience.
The trick with MailGun binary attachments is getting your HTTP client to handle multipart encoding right. I struggled at first trying to build multipart boundaries manually - don’t do that. Use a proper form-data library that handles binary streams automatically. Read your file in binary mode (not text) and let the library do the multipart work. Also, MailGun caps attachments at 25MB, so validate file size first. Their API docs are pretty basic but it’s just like any other form file upload.
I’ve used MailGun’s API a bunch and here’s what works: pass binary files as file objects, don’t try encoding them yourself. Most HTTP libraries (requests in Python, axios in Node.js) handle multipart encoding automatically if you structure the data right. Open your file in binary mode and pass it straight to the attachment parameter. Pro tip: don’t forget the filename attribute - MailGun needs this for the recipient’s email client. Make sure you’re hitting the messages endpoint with your domain in the URL path. Auth headers matter more with attachments since they’re bigger and can timeout if auth fails.