Post an MMS attachment to Text Request.

Use this endpoint to post an MMS attachment to Text Request. If successful, mms details including a mms_id unique identifier will be returned. You can use this mms_id when sending MMS messages through the API. Valid file types are csv, jpeg, png, pdf, gif, txt, xlsx, mp4, vcard, vcf. The reason for first uploading an MMS attachment is for speed during reuse. If you are sending multiple messages, you can reuse a single uploaded MMS instead of re-uploading the same attachment multiple times.

The max size for attachments is 1MB for PDFs, and 5MB for everything else, but we recommend all files stay below 1MB. Most carriers support individual files that are under 1MB. Anything larger can be sent but will be compressed in a way that affects the quality. A single message can have up to 3 attachments of any size, but the images will be downsized until the total size is no more than 2MB. PDFs can't be compressed like other images and have a max file size of 1MB.