11 error validating email via smtp helo failed

.gitignore

@@ -25,3 +25,4 @@ go.work.sum
 .env
 
 .idea/
+mailsherpa

README.md

@@ -1,6 +1,6 @@
 <br /><br />
 
-<p align="center"><img align="center" src="https://customer-os.imgix.net/companies/logos/mailsherpa_logo.png" height="144" alt="mailsherpa" /></p>
+<p align="center"><img align="center" src="https://customer-os.imgix.net/companies/logos/mailsherpa_logo.png" height="200" alt="mailsherpa" /></p>
 <h1 align="center">MailSherpa</h1>
 <h4 align="center">A CLI for verifying email address deliverability over SMTP without sending an email.</h4>
 

internal/dns/known_email_providers.toml

@@ -53,9 +53,11 @@ domains = [
     ["163.com", "netease"],
     ["263.net", "263"],
     ["263xmail.com", "263 xmail"],
+    ["antispameurope.com", "hornetsecurity"],
     ["daum.net", "daum"],
     ["gmx.net", "gmx"],
     ["haihaimail.jp", "haihai mail"],
+    ["hornetsecurity.com", "hornetsecurity"],
     ["hushmail.com", "hushmail"],
     ["icloud.com", "icloud"],
     ["mail.ru", "mailru"],

internal/mailserver/mailserver.go

@@ -115,11 +115,26 @@ func connectToSMTPviaProxy(mxServer, proxyAddress, proxyUsername, proxyPassword
 }
 
 func readSMTPgreeting(smtpClient *bufio.Reader) error {
-	_, err := smtpClient.ReadString('\n')
-	if err != nil {
-		return fmt.Errorf("Failed to read SMTP server greeting: %w", err)
+	for {
+		line, err := smtpClient.ReadString('\n')
+		if err != nil {
+			return fmt.Errorf("Failed to read SMTP server greeting: %w", err)
+		}
+
+		// Trim the line to remove whitespace and newline characters
+		line = strings.TrimSpace(line)
+
+		// Check if this is the last line of the greeting
+		if strings.HasPrefix(line, "220 ") {
+			// This is the final greeting line
+			return nil
+		} else if !strings.HasPrefix(line, "220-") {
+			// If the line doesn't start with 220- or 220, it's an unexpected response
+			return fmt.Errorf("Unexpected SMTP server greeting: %s", line)
+		}
+
+		// If it's a continuation line (starts with 220-), continue reading
 	}
-	return nil
 }
 
 func sendSMTPcommand(conn net.Conn, smtpClient *bufio.Reader, cmd string) (string, error) {