How to write the global or domin link also it should appear in mail as a click link

here is my Code I just want to know how can I write it with a mail message there shouldn't be local host it should be in a proper way 
this +encryptedVendorId is variable to concatenate with it
string emailBody = "<p>Hello,</p>"; emailBody += "<p>http://localhost:6781/public/vendorregister?id= +encryptedVendorId</p>"; emailBody += "<p>thanks</p>";