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Errors in SMTP dialog
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Errors in SMTP dialog

The Selectel mail service uses the SMTP protocol. The following SMTP dialog errors may occur when sending mail from your server to the mail host of the service.

550 bounced check filterThe email address of one of the recipients is in stop list.
If more than one recipient is listed in the email, repeat the mailing for each recipient separately to determine which address is on the stop list. If you think an address has been placed on the stop list by mistake, remove it from the stop list using API methods
501 from domain not trustedThe domain from which the email is being sent has not been added to the list of allowed senders. Make sure that the correct connected the service for the domain
421 SMTP command timeout — closing connectionThe server closed the connection because it has not been used for more than 120 seconds. To clear the error, start the SMTP dialog again

Stop list⁠

The recipient's email address goes into your local stop list if:

  • the recipient unsubscribed;
  • the recipient complained about spam;
  • email address could not be sent to.

Emails to the email addresses from the stop list are not sent, an error is returned in the SMTP-dialog 550 bounced check filter.

If you specify multiple recipients in an email and at least one of the email addresses is on the stop list, the email will not be sent to any of them. To determine which email address is on the stop list, send the email separately to each recipient.

If you believe that an address has been added to the stop list by mistake, you can remove it from the stop list using API methods.