Don't require password for SMTP connection (#739) (#740)

* don't require password

* only set when password

Author: teelur

server/BudgetBoard.WebAPI/Utils/EmailSender.cs

@@ -24,10 +24,6 @@ public async Task SendEmailAsync(string email, string subject, string htmlMessag
         }
 
         var senderPassword = Configuration.GetValue<string>("EMAIL_SENDER_PASSWORD");
-        if (string.IsNullOrEmpty(senderPassword))
-        {
-            throw new ArgumentNullException(nameof(senderPassword));
-        }
 
         var smtpHost = Configuration.GetValue<string>("EMAIL_SMTP_HOST");
         if (string.IsNullOrEmpty(smtpHost))
@@ -48,9 +44,13 @@ public async Task SendEmailAsync(string email, string subject, string htmlMessag
             EnableSsl = true,
             UseDefaultCredentials = false,
             Port = smtpPort,
-            Credentials = new NetworkCredential(senderUsername, senderPassword),
         };
 
+        if (!string.IsNullOrEmpty(senderPassword))
+        {
+            smtp.Credentials = new NetworkCredential(senderUsername, senderPassword);
+        }
+
         await smtp.SendMailAsync(mm);
     }
 }