SMTP dialog errors

Selectel mail service uses the SMTP protocol. When sending mail from your server to the service mail node, the following SMTP dialog errors may occur.

`550 bounced check filter`	The email address of one of the recipients is in the stop list. If more than one recipient is specified in the message, retry sending for each recipient separately. If the address is in a local stop list, you can find and remove the address from the local stop list
`501 from domain not trusted`	The domain from which the mail is being sent has not been added to the list of allowed senders. Ensure that you have correctly connected the service for the domain
`421 SMTP command timeout — closing connection`	The server closed the connection because it was inactive for more than 120 seconds. To resolve the error, restart the SMTP dialog
`450 ratelimit exceeded`	The rate limit for sending via the resource has been exceeded — 100 emails per five minutes for all resource domains. Wait a few minutes and retry sending