Connect any SMTP/IMAP mailbox (custom provider)

Draft — written from product facts + domain knowledge; UI labels to be verified before publishing.

If your mailbox is not on Google Workspace or Microsoft 365 — for example Zoho, Yahoo, a cPanel/web-host mailbox, an Icemail SMTP mailbox or a transactional provider such as SendGrid or Amazon SES — connect it with SMTP (for sending) and IMAP (for reading replies and running warmup). You need the host, port, username and password for both.

Prerequisites

• SMTP and IMAP are enabled on the mailbox at the provider. Many providers turn IMAP off by default.
• If the account uses two-factor authentication, an app password rather than the normal password (Gmail, Yahoo, Zoho and iCloud all require this).
• The hostnames and ports for your provider. See Common IMAP/SMTP hostnames and ports reference.

Steps

1. Go to Mailbox → Connect Mailbox.

2. Select the SMTP / IMAP (custom provider) option.

3. Fill in the sender details:

   • From name — the name recipients see.
   • Email address — the mailbox address.

4. Fill in the SMTP section:

   • Host — for example smtp.zoho.com.
   • Port — 587 (STARTTLS) or 465 (SSL).
   • Username — usually the full email address.
   • Password — the mailbox or app password.
   • Encryption — TLS/STARTTLS for 587, SSL for 465.

5. Fill in the IMAP section:

   • Host — for example imap.zoho.com.
   • Port — 993 (SSL).
   • Username and Password — normally the same as SMTP. Tick "same as SMTP" if the option is shown.

6. Click Test connection (if shown) and wait for both SMTP and IMAP to pass.

7. Click Connect / Save.

What you see afterwards

The mailbox appears in the Mailbox list as connected. Enable warmup with the Custom Mailboxes profile and set the daily campaign limit before using it as a sender account.

Tips

• Use port 587 with STARTTLS as the default; fall back to 465/SSL only if 587 is blocked.
• For transactional providers (SendGrid, Mailgun, SES) the SMTP username is a literal string such as apikey or an SMTP credential, not your email address; the IMAP side must point to a real mailbox that receives replies (for example a Google or Zoho inbox for the same address).
• Make sure the domain's SPF record includes the provider's sending servers and that DKIM is signed by the provider, otherwise mail will fail authentication.
• Icemail SMTP mailboxes come with the host, port and password shown in Icemail under the mailbox; you can also use Import from Icemail instead of entering them by hand.
• Custom SMTP mailboxes have no provider-side reputation to lean on. Warm up for a full 3 weeks and keep them at 20–30 campaign emails per day.

Troubleshooting

• SMTP authentication failed — wrong username format, a normal password where an app password is required, or SMTP AUTH disabled at the provider.
• IMAP connection timed out — IMAP disabled, wrong port (use 993), or a firewall on the provider's side. Confirm IMAP is on in the provider's mail settings.
• Connected but replies not detected — IMAP credentials point to a different mailbox than the From address, or replies are routed to a folder other than Inbox.
• Certificate error — the host name does not match the certificate; use the exact hostname from the reference article rather than an IP address or a CNAME alias.
• Works then disconnects — password rotated or provider rate limit. See Fix mailbox disconnection errors (Google, Microsoft, SMTP).

Related articles

• Common IMAP/SMTP hostnames and ports reference
• Bulk import sending accounts via CSV
• Fix mailbox disconnection errors (Google, Microsoft, SMTP)
• Connect a Google Workspace mailbox to OutreachFox
• Connect a Microsoft 365 / Outlook mailbox to OutreachFox
• Enable mailbox warmup