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ESP routing

ESP routing


Purpose


This article explains ESP routing: how to control which senders (mailboxes) can email which recipients based on the recipient’s email service provider, optional email security gateway (SEG) detection, and your campaign’s routing priority. Use it when you want to avoid risky sender-to-recipient combinations, steer Google mailboxes to Google inboxes, or enforce stricter control in Deliverability mode.


Prerequisites


  • A campaign with at least one sender (mailbox) in Sender profiles
  • Settings access on the campaign
  • For meaningful routing, contacts should have (or can receive) email provider and, when relevant, SEG intelligence—SuperSend can detect or enrich this when a contact is processed. See Email Validation in SuperSend.


Steps


  1. Open the campaign.
  2. Click Settings in the campaign area.
  3. In the settings sidebar, select Sending Rules.
  4. Under Enable ESP Routing, turn the toggle on.
  5. Choose Routing Priority:
  • Volume — SuperSend prefers senders and combinations that match your rules. If no sender fits, it can fall back so the campaign still tries to send (per in-app “How routing works” copy for this mode).
  • Deliverability — SuperSend enforces rules more strictly. Combinations that are not allowed by your rules are not used when a stricter path applies (e.g. whitelist-style behavior when you use Send rules). If no rules are defined, no emails send in this mode until you add rules or change priority.
  1. Under Routing Rules, click Add Rule for each rule you need. For each row, set:
  • From Provider — The sender’s provider bucket: All, Google, Outlook (Microsoft 365 / Outlook family in the app), Yahoo, Zoho, or Others.
  • Action — Send (allow this combination) or Do not send (block it).
  • To Provider — The recipient’s provider bucket (same options as From Provider).
  • With SEG — Any SEG, No SEG, or a specific gateway (e.g. Mimecast, Proofpoint, Barracuda, and other listed options) to match recipients behind that security filter.
  1. Order matters: Rules are evaluated from top to bottom. The first rule that matches the sender and recipient (including With SEG when set) wins. Use the delete control on a row to remove a rule, or add multiple rules and rely on first-match order.
  2. When your rules and priority look correct, save the campaign the same way you usually save changes on the campaign Settings page (e.g. save from the main campaign actions if your workflow uses an explicit save).


Modes (quick reference, consistent with the in-app “How Routing Works” panel):


  • If every rule is Do not send, the campaign runs in a blocklist style: those combinations are blocked; other combinations are allowed, subject to Routing Priority and first-match rules.
  • If you add any Send rule, Deliverability treats that as a stricter, allow-list style for who may send: only combinations that match a Send rule are used (other senders are not used for that contact when the stricter path applies). Volume still prefers matches but can fall back when nothing matches.
  • All / Any SEG match any provider or any SEG; use No SEG to target contacts without a detected security gateway on the recipient side.


Expected Result


  • When the campaign runs, sender selection for each contact’s email can filter campaign senders using your ESP routing configuration and the contact’s detected recipient provider (and SEG when applicable).
  • Behavior follows your Routing Priority and whether you use only Do not send rules or include Send rules, as described above.
  • If no sender passes routing for a contact, that send may not go out for that address until you adjust rules, senders, or the contact’s provider data.


Troubleshooting


  • Issue: After enabling ESP Routing with Deliverability and no rules, no mail goes out.

Fix: In Routing Priority, either add at least one Routing rule, switch to Volume, or turn Enable ESP Routing off. With Deliverability and zero rules, the system does not allow sends until rules exist (see “How Routing Works” on the same page).


  • Issue: A recipient’s To Provider or With SEG never matches what I expect.

Fix: Ensure the contact has gone through email validation / intelligence so the domain’s provider and SEG fields are populated. Re-run or import validation as needed, and see Email Validation in SuperSend.


  • Issue: The wrong From Provider is used for a mailbox.

Fix: Confirm the mailbox is the provider you think (e.g. Google Workspace vs Outlook). From Provider is derived from the sender’s connection (provider, address, and related signals). If rules still mis-match, adjust From Provider in the rule or use All to broaden the sender side.


  • Issue: I added several rules and results seem inconsistent.

Fix: Remember first matching rule wins. Move rows so the most important rule is first, or split conflicting cases into simpler rules.




Updated on: 27/04/2026

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