Summary of SmartRelay constraints

You should consider the following constraints when setting up and using SmartRelay:

  • SmartRelay imposes a one recipient per message limitation for injected messages. A message can be sent to only one RCPT TO address. Note that To:, Cc: and Bcc: headers are not applicable to SMTP.See Supported email messages for more details.
  • SmartRelay imposes a limit on the number of simultaneous SMTP connections between your local SMTP forwarder and your dedicated SMTP listenerSee Maximum number of simultaneous SMTP sessions for more details.
    • By default, we apply an inbound rate up to 4 msg/sec.

    See Inbound rate limiting at the SMTP listener for more details.

  • You can attach documents to emails, but consider that this can have a negative impact on deliverability. If necessary, consider a maximum of 10MB total size.
    NOTE: Attachments are not saved like each single email.
  • If you enable the creation of new deliveries option during setup, new deliveries are sent as TRANSACTIONAL or NEWSLETTER, according to the default that is set during configuration. See Managing deliveries by type and category and Delivery identifier, label and category > X-Clab-SmartRelay-NewDeliveryType for more details.
    Note: It is important that you always specify whether the delivery should be TRANSACTIONAL or NEWSLETTER (a bulk or marketing delivery), as this affects suppression list management.
  • If link tracking is enabled, it is applied to all links in your emails. You can control individual messages using headers. See View and link tracking options, Enabling tracking and custom domains and Tracking for more details.
  • See SMS Message Requirements for more about SMS message constraints

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