Set up

Goal

A third-party sending service delivering your sequence emails while replies keep landing in your own mailbox, with a clear picture of which bounces Reply can see and which it cannot.

Preconditions

• An account with the sending service, and the credentials it issues for SMTP.
• A mailbox on a business domain to receive on; the corporate-domain rule applies to both

halves of a split setup, and the general connection flow is covered in Connect a mailbox.

• For bounce detection, an administrator on the sending service who can add a webhook.

Steps

1. From Settings → Email Accounts → New email account, choose Other Provider, then switch on I want to use different email servers for sending and receiving emails. One form stands behind every non-native setup: outgoing mail leaves through the service's SMTP server, incoming mail keeps being read from your own mailbox over IMAP, and the Reply to field decides where answers land.
2. For SendGrid, the sending side takes smtp.sendgrid.net as the host, the literal word apikey as the user name, and your SendGrid API key as the password. The receiving side keeps your real mailbox's IMAP settings, not SendGrid's.
3. To have SendGrid bounces flow back, add Reply's endpoint as an Event Webhook in SendGrid. This connection belongs to one user rather than to the whole team, and automatic bounce detection is not switched on for every workspace: ask support to confirm yours before treating silence as a data problem. SendGrid's own platform also caps how many event webhooks one account may hold, which is worth checking if the webhook cannot be added.
4. Understand which SendGrid events count. A Bounce is recorded, resolved to hard or soft from the reason the receiving server gave. A Spam report is recorded as a bounce flagged as a complaint. A Dropped event counts only when the drop was caused by the recipient: an address SendGrid already knows as bounced or invalid, or a spam-related drop; drops caused by your own SendGrid configuration, and drops for addresses globally unsubscribed inside SendGrid, are left out. A Deferred event is treated as temporary and nothing is recorded. Matching relies on data attached at send time, so only emails sent after the webhook went live can ever be matched.
5. Watch for the webhook going into Error. A failed daily check flips it, notifies the mailbox owner in the Notification Center and by email from Reply's support address, and stops bounce recording for that SendGrid account until a later check succeeds.
6. For Mailgun and every other SMTP relay, plan on handling bounces yourself. The bounce is delivered to the relay's own infrastructure, while Reply reads replies over IMAP from a different mailbox entirely, so it never sees it. Export the bounce list from the provider, bring it in as a CSV (see Import contacts) and mark those contacts as Bounced, drop them into a list, or blacklist them.
7. For Zapmail, run the export from the Zapmail side using the Reply API key found under Settings → API Key. That key identifies one user in one workspace, so export with the key of the account the mailboxes should belong to. On volume-based plans, an export that would take you past your mailbox allowance produces a confirmation step and a billing summary before it completes.
8. Treat MailToaster as a second, separate job. Sending Zapmail mailboxes into Reply does not place them in MailToaster; that is another export from Zapmail, and it needs the MailToaster account already linked to Reply.

> Free and disposable domains are refused for sending. gmail.com, yahoo.com, outlook.com, > hotmail.com and thousands of other free and throwaway providers are checked against both > the mailbox address and the sending address, so an alias whose SMTP address sits on a free > domain is turned away even when the receiving mailbox is a corporate one. The same > addresses remain perfectly valid as the login you sign in to Reply with.

Expected result

The account appears in your Email Accounts list, the sending and receiving tests both come back green, and mail leaves through the service while replies appear in your Reply inbox.

Verification

Assign the account to a sequence and let one step go out, then compare: the message should appear in the sending service's own activity log and arrive at the recipient with your domain in the From address. To confirm SendGrid bounce detection, send to an address you know is dead after the webhook is live and check the contact picks up a bounced status in Reply. For a relay without detection, confirm the opposite; the bounce appears on the provider's dashboard and nowhere in Reply.

What happens next

Bounce data drives contact statuses and sequence stopping, so a relay without detection leaves those statuses incomplete until you import the list. See bounce handling and email validation for how Reply uses them. New sending infrastructure also needs volume discipline from day one: set each mailbox's daily figure before pointing real sequences at it, per Configure sending limits, and read email warm-up before moving existing volume onto a fresh relay.

Common mistakes

• Waiting for Mailgun bounces to appear in Reply; they never arrive, however long you leave it.
• Connecting a SendGrid webhook and expecting it to explain last month's bounces; only sends made after it went live can be matched.
• Exporting Zapmail mailboxes into Reply and assuming MailToaster received them too.
• Putting a free address in the SMTP half of an alias setup; both addresses are checked, and the refusal names the mailbox rather than the sending address.
• Trying a free address through the Gmail or Outlook single-click route. The provider's consent screen completes first, and only then does Reply return you to the mailbox list with a note about using a work address on a corporate domain; nothing was connected and nothing is broken.

Related

• Connect a mailbox
• Bounce handling · Email validation
• Purchased mailboxes are still pending
• Set up opt-out and unsubscribe

Build with Reply

• REST API: docs.reply.io – the same API key a Zapmail export uses, taken from Settings → API Key