Sending mail with attachment not working

Question

I used SKPSMTPMESSAGE to send mail from my application. Problem is i am getting error while sending mail with attachment. Any one send mail successfully with attachment using SMTPSender.[message appendFormat:@"Content-Transfer-Encoding: %@\r\n\r\n", [part objectForKey:kSKPSMTPPartContentTransferEncodingKey]] give me a null value. Encoding used here is base64. Can any one help me? Thanks in advance!!!