I replaced the different cdosys.dll with the one from xp with no change, same error. I switched from vbsendmail to cdo, about a year ago because users were have to much difficulty with all the options in vbsendmail. My software is roof estimating and the users are not computer wizes. With the problem with vista and probably more in windows 7 it looks like i might to switch to something else, maybe a 3rd party ocx or ? This has sure become a major unexpected hurdle with making my app work on vista. Emailing rtf attachments (Contracts, Invoices, Purchase Orders, etc) is a nice feature with my app and I cannot abandon it. I sure do appreciate all the feedback and help.