discussion Guide Plesk Plesk Panel SMTP Error: “5.7.0 Must issue a STARTTLS command first” Fix Guide 2025

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Plesk Panel SMTP Error: “5.7.0 Must issue a STARTTLS command first” Fix Guide 2025​

When configuring SMTP mail settings in XenForo or any other application, you may encounter the following error:

SMTP 5.7.0 Must issue a STARTTLS command first

This error indicates that the server does not allow communication without TLS (encrypted connection).
If your SMTP client does not support TLS or requires a different configuration, you may need to disable this enforcement on your Plesk server.

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🔧 Solution: Edit Postfix Configuration​

• Connect to your server via SSH.
• Edit the following file:

nano /etc/postfix/master.cf

• In the appropriate section, add or edit the following lines (they may already exist — just modify them as needed):

smtpd_enforce_tls=no
smtpd_tls_security_level=may

To find the parameters quickly, use CTRL + W, type smtpd_enforce_tls, and then modify the existing value.

Both smtpd_enforce_tls and smtpd_tls_security_level should be adjusted in their respective entries.

These settings remove the STARTTLS enforcement and make TLS support optional.

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🔁 Reload the Postfix Service​

service postfix reload

 

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If you encounter any other issues related to this topic, please remember to open a support ticket on our website!