I have simple piece of code which does not work

oMsg = createobject("CDO.Message")

oMsg.To = "aa@bb.com"
oMsg.Subject = "aaaaa"
oMsg.AddAttachment("c:\autoexec.bat")
oMsg.Send

Return error code is

OLE IDispatch exception code from ?:The message could not be sent to SMTP server.
The transport error code was 0x80040217. The server response was not available.

Any sugestion?

Incoming mail server is IMAP.

Thanks in advance.