Errors

Any non-2xx response raises an error. The Ruby error tree the rbgo binding exposes mirrors the Go APIError from go-dimail:

Dimail::Error      < StandardError   # base
Dimail::APIError   < Dimail::Error   # any non-2xx response

Dimail::APIError carries:

Member	Meaning
#status	the HTTP status code (Integer)
#detail	the parsed FastAPI detail (String / Array / Hash, or nil)
#body	the raw response body (String)
#not_found?	status is 404
#unauthorized?	status is 401
#forbidden?	status is 403
#conflict?	status is 409

begin
  client.post_domain({ "name" => "new.gouv.fr", "features" => ["mailbox"] })
rescue Dimail::APIError => e
  raise unless e.conflict?
  warn "domain already exists"
end

In Go

Session#Call returns the underlying *godimail.APIError unchanged, so the same information is available with errors.As:

_, err := s.Call(ctx, "get_domain", "absent.example")
var apiErr *godimail.APIError
if errors.As(err, &apiErr) && apiErr.NotFound() {
    // handle 404
}