Some providers, such as Orange, Wanadoo, and Oléane, limit the number of simultaneous connections into their servers to prevent transformation of any random machine to a spambot. Thus, you cannot send mails. The emails are queued in IMSVA and the following error message shows:
Host <Service Provider's MTA> refused to talk to me: 421 .... Too many connections, slow down.
As a result, only authorized providers (Orange, Free.fr, 9Tel, and other main foreign providers) can send more than the limit.
To avoid this limitation, use the mail server from your provider as a relay/smarthost for the domains:
- Navigate to Administration > IMSVA configuration > SMTP Routing > Domain-based Delivery.
- Add the following:
- Destination domain
- Mail server of your provider (FQDN or IP)
- Related port, which is normally port 25