Improved feedback: Notify when the same email file is being reused, and whether or not that invite was sent to new subscribers

main.go

@@ -284,6 +284,13 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 		}
 	}
 
+    existingReaderCount := len(sentToAddresses)
+    newReaderCount := 0
+
+    if existingReaderCount > 0 {
+        fmt.Println("Same email file specified: Sending only to new subscribers...")
+    }
+
 	var group []string
 	for _, a := range audience {
 		if a == "" {
@@ -309,6 +316,7 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 				for i, res := range results {
 					log.WriteString(fmt.Sprintf("%s: %s\n", group[i], res.Message))
 				}
+                newReaderCount += len(group)
 				group = group[0:0]
 			}
 		}
@@ -324,6 +332,16 @@ func blastMail(cfg *Config, logFile string, trackingFile string, audience []stri
 		for i, res := range results {
 			log.WriteString(fmt.Sprintf("%s: %s\n", group[i], res.Message))
 		}
+        newReaderCount += len(group)
+	}
+
+    if newReaderCount > 0 {
+        newSubscribers := existingReaderCount > 0
+        if newSubscribers {
+            fmt.Printf("Sent to %d new subscribers!\n", newReaderCount)
+        }
+    } else {
+        fmt.Printf("Not sent (no new subscribers)\n")
     }
 }