Create a Lookup to use mailto formula

To allow a lookup to return a mailto hyperlink in the signature configuration.

1. Create a new lookup - Signature Configuration > Lookup Configuration > Select +New Lookup

2. Select Formula Lookup and paste in the mailto formula below.

Formula for mailto below

string strMail;
string strFormat;
strFormat = "(!format!)";
strMail = "(!email!)"; 
if (strMail == "") 
{ 
 return ""; 
} 
else 
{
   if(strFormat=="1")
   { 
  return "eMail: "+ "" + strMail + "";
} 
    else
    { 
        return "eMail: " + strMail;
    }
} 

Save and Send test email.