By default W-ELP will use the PowerShell features to send e-mails. The configuration can be done using the e-mail "Configure" dialog from within the Admin tab. The text based config file MailConf.ini which can be found in the Workpath folder (e.g. c:\ProgramData\WELP) controls the sending of e-mails and can be adapted e.g. to use other SMTP clients like PowerShell Core or even Blat.
If you need to use the depreciated utility Blat for sending e-mails please download the blat legacy package and follow the instructions provided by the ReadMe.pdf.
Related articles: E-Mail/Fax sending out the job as Tiff / PDF