邮件附件格式

if(ObjMailTask.AnnexFile!="")//添加附件
{
System.Net.Mime.ContentType type = new System.Net.Mime.ContentType("application/vnd.openxmlformats-officedocument.wordprocessingml.document");
System.Net.Mail.Attachment objAtt = new System.Net.Mail.Attachment(ObjMailTask.AnnexFile, type);
ObjMail.Attachments.Add(objAtt);
ContentDisposition disposition = objAtt.ContentDisposition;
disposition.DispositionType = "attachment;\t filename=" + Path.GetFileName(ObjMailTask.AnnexFile);
}

邮件原文格式
-----------=_VxiQcghCADTbNqgPmLRpqAGvcowuwOnorRmShm
Content-Type: application/octet-stream; 内容是应用，即附件
name="aa.doc" 附件应用名
Content-Transfer-Encoding: base64 编码格式
Content-Disposition: attachment; 内容描述：附件
filename="aa.doc"