Title: StartTLS problem
Last modified: February 2, 2024

---

# StartTLS problem

 *  Resolved [bluelemonade](https://wordpress.org/support/users/bluelemonade/)
 * (@bluelemonade)
 * [2 years, 4 months ago](https://wordpress.org/support/topic/starttls-problem/)
 *     ```wp-block-code
       I'm having problems connecting to an MS SMTB server. StartTLS is probably not recognized by the client. What could be the reason
   
       Debug:Email source WP Mail SMTPMailer: Other SMTP serverSMTP Error: Could not connect to SMTP host. STARTTLS command failed Unrecognized command
   
       SMTP debugging:2024-02-02 09:58:28 Connection: opening to mail.ethianum.de:587, timeout=300, options=array()
   
       2024-02-02 09:58:28 Connection: opened
   
       2024-02-02 09:58:28 SERVER -> CLIENT: 220 ETHHD-EX01.ethianum.local Microsoft ESMTP MAIL Service ready at Fri, 2 Feb 2024 10:58:27 +0100
   
       2024-02-02 09:58:28 CLIENT -> SERVER: EHLO wordpress.ethianum-klinik-heidelberg.de
   
       2024-02-02 09:58:28 SERVER -> CLIENT: 250-ETHHD-EX01.ethianum.local Hello [85.13.163.89]250-SIZE 102400000250-PIPELINING250-DSN250-ENHANCEDSTATUCODES250-X-ANONYMOUSTLS250-AUTH GSSAPI NTLM250-X -EXPS GSSAPI NTLM250-8BITMIME250-BINARYMIME250-CHUNKING250-XEXCH50250-XRDST250 XSHADOW
   
       2024-02-02 09:58:28 CLIENT -> SERVER: STARTTLS
   
       2024-02-02 09:58:34 SERVER -> CLIENT: 500 5.3.3 Unrecognized command
   
       2024-02-02 09:58:34 SMTP ERROR: STARTTLS command failed: 500 5.3.3 Unrecognized command
   
       SMTP Error: Could not connect to SMTP host. STARTTLS command failed Unrecognized command
   
       2024-02-02 09:58:34 CLIENT -> SERVER: QUIT
   
       2024-02-02 09:58:34 SERVER -> CLIENT: 221 2.0.0 Service closing transmission channel
   
       2024-02-02 09:58:34 Connection: closed
   
       SMTP Error: Could not connect to SMTP host. STARTTLS command failed Unrecognized command
       ```
   

Viewing 3 replies - 1 through 3 (of 3 total)

 *  Plugin Support [Darshana](https://wordpress.org/support/users/darshanaw/)
 * (@darshanaw)
 * [2 years, 3 months ago](https://wordpress.org/support/topic/starttls-problem/#post-17395262)
 * Hi [@bluelemonade](https://wordpress.org/support/users/bluelemonade/),
 * Thanks for reaching out! This error indicates that the SMTP server you are trying
   to connect to does not support the STARTTLS command.
 * Please get in touch with your email provider with the full error log, and they
   should be able to assist you further.
 * In the meantime, I would suggest you configuring an [alternative mailer](https://wpmailsmtp.com/docs/a-complete-guide-to-wp-mail-smtp-mailers/)
   on your WordPress site.
 * I hope this helps. Thanks!
 *  Thread Starter [bluelemonade](https://wordpress.org/support/users/bluelemonade/)
 * (@bluelemonade)
 * [2 years, 3 months ago](https://wordpress.org/support/topic/starttls-problem/#post-17398510)
 * Strange, I can of course connect to all kinds of mail programs and TLS / StartTLS.
   Only the plugin doesn’t work.
 *  Plugin Support [Darshana](https://wordpress.org/support/users/darshanaw/)
 * (@darshanaw)
 * [2 years, 3 months ago](https://wordpress.org/support/topic/starttls-problem/#post-17406997)
 * Hi [@bluelemonade](https://wordpress.org/support/users/bluelemonade/),
 * Please kindly know, that the WP Mail SMTP plugin just bridges a connection between
   your WordPress site and your preferred email mailing service (Eg: SendLayer, 
   Brevo, SMTP.com, or your private email provider).
 * This error suggests that your web server is unable to establish a connection 
   with your SMTP host. To resolve this issue, please contact your hosting or email
   support team along with the complete error log, and they should be able to assist
   you further in resolving the problem.
 * Thanks!

Viewing 3 replies - 1 through 3 (of 3 total)

The topic ‘StartTLS problem’ is closed to new replies.

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 * 3 replies
 * 2 participants
 * Last reply from: [Darshana](https://wordpress.org/support/users/darshanaw/)
 * Last activity: [2 years, 3 months ago](https://wordpress.org/support/topic/starttls-problem/#post-17406997)
 * Status: resolved