yes, I am using that, however Apple mail does not like the mime data built by libmailcore. My emails are received fine in the other end, but in the senders end, in sent items folder of mail, it shows a text dump of the entire RFC 822 data instead of rendering it as an email. I am seeing that mail core is using a multipart/alternate mime type which is grouping a HTML and text representation of the body, in my tests this is what Apple doesn't like. They actually use a slightly different mime ver.

Thanks will check this out..

Any tip on any API or Library to use for this purpose?

Thanks for your comment. May be I will have to find a way to circumvent this. Any suggestions?