Recommended settings for a local SMTP forwarder

We recommend that you use the following settings for your SMTP forwarder:

  • Configure the dedicated IP address that Contactlab assigns to your stream as a smarthost. Ensures that every message will be forwarded to that address.
  • Set the timeout on the SMTP connection to at least 300 seconds
  • Limit the number of simultaneous outbound SMTP connections to eightThe limit is configurable. Please let us know your needs.
  • Set the number of messages sent in a single connection to a reasonable limit, for example, 100We do not limit the number of messages delivered in a single connection, unless you require a specific setting. However, by doing this on your SMTP forwarder, you will usually help it manage its own outbound queue more smoothly.


  • You do not need to configure SMTP-AUTHWe use the IP address(es) that you provide to us to limit inbound traffic.
  • You do not need to setup DKIM signingWe sign your messages when delivering them to their destination.

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Using SmartRelay