> ## Knowledge Base Index > Fetch the complete knowledge base index at: https://help.supersend.io/sitemap.xml > Use this file to discover available pages before exploring further. > Pure-Markdown content can be obtained by appending a '.md' suffix to the content URLs listed in the sitemap (without the trailing slash). # 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](https://help.supersend.io/en/article/email-validation-in-supersend-umb5lo/). ## 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. 6. 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. 7. **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. 8. 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](https://help.supersend.io/en/article/email-validation-in-supersend-umb5lo/). - **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. ## Related articles - [Campaigns Overview](https://help.supersend.io/en/article/campaigns-overview-106g6l9/) - [Create a Campaign](https://help.supersend.io/en/article/create-a-campaign-18zo2cn/) - [Create and Use Sender Profiles](https://help.supersend.io/en/article/create-and-use-sender-profiles-1g4rjqt/) - [Email Validation in SuperSend](https://help.supersend.io/en/article/email-validation-in-supersend-umb5lo/)