--- title: "ESP Matching" description: "ESP matching is an optional sequence setting that sends each email from a mailbox on the same provider as the lead. Learn how it works, its pros and cons, and when to use it." url: https://help.salesforge.ai/en/articles/10333549-esp-matching collection: "Sequencing Guide 🔨" updated: 2026-11-03 language: en --- # ESP Matching ESP matching is an optional sequence setting that sends each email from a mailbox on the same provider as the lead. Learn how it works, its pros and cons, and when to use it. ## What is ESP matching? ESP matching is an optional email setting for sequences. When it is on, Salesforge tries to send each email from a mailbox hosted by the same email service provider (ESP) as the lead: a Gmail lead is sent from a Google mailbox, and an Outlook / Microsoft 365 lead is sent from an Outlook mailbox. **Do we recommend it? Not by default.** The feature works as described below, but matching the provider does not guarantee better deliverability, and in some setups it can make results worse. We recommend leaving it off unless you have a specific reason to use it (see "When to use it and when to avoid it" below). ## How to turn it on or off 1. Open your sequence and go to **Settings**. 2. Under **Email only**, find **Deliverability** and switch **Email service provider (ESP) matching** on or off. ![ESP matching toggle in the sequence settings under Email only > Deliverability](https://staticfiles.gleap.io/p677a7ec3b682e732d0e54ed0/XlJAsA5nas0U0AzRKnATxpS7G0JIaf8GIq1knkzSdFfcm6tZnpoe176N76uUmxpI9yKUXkVBB6V.png) The setting is per sequence, so you can use it on one sequence and keep it off on others. **Plan availability:** ESP matching is not available on the Pro plan. ## How it works - **Only Gmail and Outlook are matched.** Mailboxes are grouped by provider (Google or Outlook / Microsoft 365). Leads on any other provider, or leads whose provider is unknown, have no match. - **Capacity decides which matching mailbox is used.** For a Gmail or Outlook lead, Salesforge picks a mailbox on the same provider that still has daily sending capacity left, generally favouring mailboxes with more capacity remaining. - **If there is no match, it falls back.** When no matching mailbox has capacity, or the lead's provider is not Gmail or Outlook, the email is sent from any other mailbox in the sequence that still has capacity. It is not blocked. - **Mailforge and other SMTP/IMAP mailboxes are not tied to Gmail or Outlook.** They are never a "match", so they are used as the fallback. For example, with Google and Mailforge mailboxes, Gmail leads go to your Google mailboxes while Outlook and all other leads go to your Mailforge mailboxes, as long as the Google mailboxes have capacity. - **It applies to the first email only.** Follow-ups in an existing conversation keep using the mailbox that started it, so matching is not applied to them. - **Validation helps.** Salesforge detects a lead's provider from the email domain (its MX records) when the email is validated. Leads that were not validated have no known provider and cannot be matched. ## Example scenarios **Example 1: enough matching capacity** - 50 Gmail leads and 50 Outlook leads. 2 Gmail mailboxes (40 capacity in total) and 3 Outlook mailboxes (60 capacity in total). - 40 Gmail leads are sent from Gmail mailboxes and all 50 Outlook leads from Outlook mailboxes. The remaining 10 Gmail leads fall back to Outlook mailboxes that still have capacity. **Example 2: unknown providers** - 100 Gmail leads and 20 leads with an unknown provider. 2 Gmail mailboxes (40 capacity) and 4 Outlook mailboxes (80 capacity). - 40 Gmail leads are sent from Gmail mailboxes. The other 60 Gmail leads and all 20 unknown leads are sent from the Outlook mailboxes, because nothing else has capacity. **Example 3: not enough capacity overall** - 50 Gmail, 50 Outlook and 20 unknown leads. 2 Gmail and 2 Outlook mailboxes, each able to send 20 emails per day (80 in total). - 40 Gmail and 40 Outlook leads are scheduled. The rest, including the unknown leads, wait because no mailbox has capacity left. They are picked up on following days as capacity frees up. ## Pros - **Controlled routing.** You decide which kind of mailbox reaches which kind of lead, for example Google mailboxes for Gmail leads and a different set of mailboxes for everyone else. - **A way to test.** If one provider performs worse for you (Outlook recipients are a common case, as deliverability there is harder across the industry), matching lets you compare Outlook-to-Outlook against your normal setup. - **Predictable fallback.** Emails are not blocked when no match is available, they are sent from another mailbox. ## Cons - **No guaranteed deliverability gain.** Sending from the same provider does not make an email more likely to reach the inbox. Content, list quality, sending volume and mailbox health matter far more. - **It can push more volume through weaker mailboxes.** In our experience Google mailboxes usually perform better than Microsoft 365 ones. With matching on, all your Outlook leads are sent from Outlook mailboxes, so more of your sending depends on the provider that tends to be harder to land in the inbox. - **Uneven mailbox use.** If most of your leads are on one provider, that provider's mailboxes are used up first while the others sit idle until the fallback kicks in. - **Fewer mailboxes per lead.** With a small number of mailboxes, matching limits which ones can send to each lead. Combined with other limits such as sequential sending, this can slow down how fast emails are scheduled. - **Leads with an unknown provider.** Unvalidated or unsupported leads cannot be matched, so the setting does not apply to them. Check the contacts list if the number of sent emails looks lower than expected. ## When to use it and when to avoid it **Consider turning it on when** you have a mix of Google and Microsoft 365 mailboxes with plenty of capacity on both, you want to test whether Outlook-to-Outlook or Gmail-to-Gmail sending works better for your list, or you deliberately want a split such as Google mailboxes for Gmail leads and other mailboxes for the rest. **Keep it off when** you are troubleshooting low inbox placement or open rates, you use mostly one provider's mailboxes, you have only a few mailboxes, or sends are slower than expected. If your results dropped after you enabled it, turn it off and compare. Whatever you choose, test on a small part of your volume first, and compare the results by provider in your sequence analytics before rolling the setting out to every sequence. ## Summary ESP matching sends Gmail leads from Google mailboxes and Outlook leads from Outlook mailboxes, and falls back to any mailbox with capacity when there is no match. It is an optional control, not a deliverability booster, and we do not recommend it by default.