Make sure that dll is on the pass and there's no other dll with the same name on the path.
BTW, is there any reason that you're using DLL instead of MAPI class?

>I copied the sendmail dll to the same directory
> of my application.
>
>
> I created a test button and when I press it I see the message:
>
> Cannont find entry point sendMail in the dll
>
>
> I put the folling test code in click event of the button
>
>
>
> *This DLL is identical to the SendMail method of MAPIMail class.
>
>*The parameters are in the same sequence - there are no optional parameters.
>
>*Example of usage:
>
>DECLARE Integer SendMail IN SendMail ;
> String cProfileName, ;
> String cPassword, ;
> String cRecipientList, ;
> String cSubject, ;
> String cBodyText, ;
> String cAttachmentList, ;
> Integer nRequestReceipt, ;
> Integer nShowClient
>
>nResult=SendMail("","","bobby@hillbilly.com","test subject","text","",0,0)
>
>
>*The RecipientList and AttachmentList can both contain multiple entries -
>*they MUST be separated by commas - you can't yet use semi-colons as in the
>*MAPI class.
>
>*The RecipientList at the moment cannot contain cc or bcc recipients - this will
>*follow in a later version.
>
>*Avoid sending 1 as ShowClient - if the user closes or cancels the action, an
>*error will be presented - this is unavoidable and, as the purpose of this is
>*actually for background sending, should be unnecessary.
>
>*If you do use this DLL and would like to receive updated versions automatically,
>*send an eMail to SendMail.Updates@NBCSoftware.com and you will be added to the list.