Have you called the ResolveName() method? Check the article on my website under Q&A/General/qGEN015

>I am having particular difficulty with one particular computer. When trying to use sendmail() from the Mapimail class I get the error:
>OLE Dispatch exception code 0 from MAPIMessages:
>Unknown recipient.
>
>We use ms exchange for our company email system and for the recipient field in the sendmail call, we just put the name of the person who it is intended for as listed in the exchange address list.
>It works on all the other machines, I don't know what is different with this one.