github.com/domodwyer/mailyak (go): Package mailyak provides a simple interface for generating MIME compliant emails, and optionally sending them over SMTP.  Both plain-text and HTML email body content is supported, and their types implement io.Writer allowing easy composition directly from templating engines, etc.  Attachments are fully supported (attach anything that implements io.Reader).  The raw MIME content can be retrieved using MimeBuf(), typically used with an API service such as Amazon SES that does not require using an SMTP interface.
Keywords: attachment|email|go|golang|mime|smtp