HTTP 422
Attachment Invalid Encoding
One or more attachments contain invalid base64 content. Ensure each attachment's content field is standard base64-encoded (RFC 4648) with no line breaks.
Example response
{
"type": "https://email.squibble.ch/docs/errors/messages/send/attachment-invalid-encoding/",
"title": "Attachment Invalid Encoding",
"status": 422,
"detail": "...",
"instance": "/api/v1/..."
}