E-mail guidelines

E-mail standards

The following applies to the delivery of Internet e-mails through the Proximus network:

  • Proximus mail servers will not accept connections from unsecured systems. These include open relays, open proxies, open routers, or any other system that has been determined to be available for unauthorized use.
  • Proximus mail servers will not accept connections from systems that use dynamically assigned or residential IP addresses.
  • Proximus mail servers will reject connections from any IP address that does not have a reverse DNS (PTR).
  • Proximus may reject connections or mails from senders whose recipient lists consistently generate a higher than 10% bounce failure rate (i.e. over 10% of a sender's mailing list is destined for users that do not exist on our systems).
  • Proximus may reject connections or mails from senders who are unable to accept bounce-return messages destined for their domain.
  • If you are using our webmail solution, you can include up to 25 addressees per e-mail.
  • If you are using an e-mail client, you can include up to 100 addressees per e-mail.
    Please note: on other networks than the Proximus network, you are limited to 10 e-mail addresses simultaneously per e-mail via an e-mail client.

Technical requirements

  • Sender is expected to comply with all technical standards for the transmission of Internet e-mail, as published by The Internet Society's Internet Engineering Task Force (IETF), including RFC 2821, RFC 2822, and others.
  • After given a numeric SMTP error response code between 500 and 599 (also known as a permanent non-delivery response), the sender must not attempt to retransmit that message to that recipient again.
  • Sender must not open more than 4 simultaneous connections to Proximus inbound e-mail servers without making prior arrangements.
  • The mechanism for unsubscribing, either from individual lists or all lists hosted by the sender, must be clearly documented and easy for recipients to find and use.
  • Connections from dynamic IP space may not be accepted.
  • E-mail servers must be secured to prevent unauthorized or anonymous use.
  • E-mail servers must have valid reverse DNS records.