sendgrid/sendgrid-python — pull request #5 by emtrane (2012-07-27 00:53:51+00:00)
Title: Don't include a Content-Disposition header when cid is provided

Providing both a Content-ID header and Content-Disposition header
with type 'attachment' confused some email clients. If no
Content-Disposition header is given, it defaults to 'inline'
which is what is desired when using cids.