Google Workspace costs $6/inbox/month. At 50 inboxes, that's $300/month or $3,600/year just in infrastructure before you've sent a single sequence. Inframail charges $99/month flat for unlimited Microsoft-hosted inboxes. Connect those to Instantly's sending platform and you've cut your stack cost to a fraction of what most teams spend on inbox setup alone.

By Rishabh Ambasta, Founder, Modern Inbound.

This guide covers the exact steps: credential export from Inframail, CSV import into Instantly, the port settings that trip most first-time setups, and the warm-up workflow you can't skip if you want your domains to last past month two.

What This Integration Does

Inframail creates Microsoft-hosted SMTP inboxes on your custom domains at a flat monthly rate. Instantly is the cold email sequencing platform that sends campaigns through those inboxes. The connection is SMTP/IMAP-based: Inframail exports credentials as a CSV and you import that into Instantly's Accounts section. No API handshake. No live sync.

Microsoft-hosted inboxes are the right call for cold outreach infrastructure in 2026. Google has aggressively flagged and suspended Workspace accounts used for high-volume cold email over the past year. Inframail's Microsoft infrastructure is more resilient for teams sending at volume. That's just what works for outbound prospecting right now.

One practical note: every new batch of inboxes you create in Inframail requires a manual re-export and re-import into Instantly. For most teams adding inboxes monthly, that's a 10-minute task. For teams rotating hundreds of inboxes a week, it becomes a workflow to document and delegate.

What You Need Before You Start

Four things must be in place before the import works: an active Inframail account, custom domains with DNS records fully propagated and verified in Inframail's dashboard, an Instantly Growth plan or above, and the SMTP credentials CSV exported from Inframail. If your SPF, DKIM, DMARC, or MX records aren't verified yet, Instantly returns authentication errors that look like password failures. They're not.

Inframail paid subscription (any plan includes unlimited inboxes)
Custom domains in Inframail with DNS verification complete: SPF, DKIM, DMARC, and MX all green
Instantly Growth plan ($37/month billed annually) or higher for unlimited sending accounts
SMTP credentials CSV from Inframail's Export Accounts section

DNS propagation takes 24 to 48 hours. Don't start the Instantly import until every record shows green in Inframail. Rushing this step accounts for more troubleshooting time than any other part of the setup.

How to Connect Inframail Inboxes to Instantly: 6 Steps

The full setup takes under 20 minutes for a batch of 20 inboxes. Skipping Step 6 (warm-up) is the most common reason sender reputation drops within the first 30 days. It's not optional.

Add your domain in Inframail. Go to Domains, add each outreach domain, copy the generated SPF, DKIM, DMARC, and MX records into your registrar, and wait for all four to verify.
Create inboxes in Inframail. Navigate to Inboxes and create accounts using a consistent format like first.last@domain.com. Inframail provisions Microsoft-hosted SMTP credentials for each one automatically.
Export SMTP credentials. Click Export Accounts from the Inframail dashboard. The CSV includes email address, SMTP host, SMTP port, IMAP host, IMAP port, and password per inbox. Store it securely.
Import into Instantly. In Instantly, go to Accounts and choose Add Accounts via CSV. Upload the Inframail file. Before confirming, verify the port mapping: SMTP must be 587 with STARTTLS, not 465 with SSL. This mismatch causes most import failures.
Run the connection test. Instantly tests each inbox after import. Any inbox with a red status has a wrong credential or unresolved DNS issue. Fix those before adding any failing inboxes to campaigns.
Activate warm-up per inbox. Enable Instantly's email warm-up for every new inbox. Start at 20 to 30 warm-up sends per day for at least 3 weeks before sending cold campaigns. Skip this and you'll burn the domain within 60 days.

Common Errors and Fixes

Three issues cause most failed imports: wrong SMTP port (Inframail uses 587 with STARTTLS, not 465 with SSL), passwords with commas or quotes breaking CSV parsing, and running the import before DNS has fully propagated. All three are fixable in minutes once identified.

Error	Cause	Fix
Authentication failed on import	Wrong SMTP port or SSL vs. STARTTLS mismatch	Set SMTP port to 587, STARTTLS enabled. Not 465.
CSV import fails mid-file	Password contains a comma or quote character	Wrap the password cell in double quotes in the CSV, or reset the password in Inframail to remove special characters.
Connection test fails post-import	DNS not fully propagated	Reconfirm all four DNS records are green in Inframail. Wait the full 48 hours, then retry the import.
Emails land in spam after connecting	DMARC set to p=reject before warm-up completes	Set DMARC to p=none during warm-up. Move to p=quarantine after 30 days of consistent sending.

What Syncs Between Inframail and Instantly

Inframail and Instantly don't share live data after the initial credential import. Instantly owns all campaign-side data: opens, clicks, replies, bounces, and unsubscribes. Inframail owns the inbox infrastructure. Delete an inbox in Inframail and you need to remove it from Instantly manually. No webhook. No real-time sync.

Data Type	Where It Lives	Syncs Automatically?
SMTP/IMAP credentials	Inframail (source), Instantly (imported copy)	No. Manual re-import required.
Email opens and clicks	Instantly only	No
Reply data	Instantly only	No
Bounce notifications	Instantly only	No
Warm-up score	Instantly only	No
Domain DNS status	Inframail only	No

The absence of live sync isn't a flaw. Inframail is infrastructure. Instantly is execution. Two separate systems with separate responsibilities is the right architecture for cold email at scale.

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Frequently Asked Questions

Does Inframail have a native integration with Instantly?

No. There's no native connector or OAuth flow between Inframail and Instantly. You export SMTP credentials as a CSV from Inframail and import them into Instantly's Accounts section. It's a one-time manual import per batch of inboxes, with a re-import required whenever credentials change.

Which Instantly plan do I need to connect Inframail inboxes?

You need Instantly's Growth plan at $37/month billed annually, or higher. The free trial limits how many sending accounts you can connect. Growth includes unlimited sending accounts, which is the right tier for 20 or more Inframail inboxes.

How many Inframail inboxes should I connect to Instantly?

Start with 3 to 5 inboxes per domain, sending 20 to 30 warm-up emails per inbox per day. For a team targeting 1,000 new prospects a week, 20 to 30 warmed inboxes across 5 to 8 domains is a workable baseline. Scale inbox count before scaling daily send volume.

What happens in Instantly if I reset a password in Inframail?

The inbox connection in Instantly breaks immediately. You'll see an authentication error in your Accounts dashboard. Update the credential manually in Instantly by editing the affected account and entering the new password. There's no auto-sync, so every password change in Inframail requires a manual update in Instantly.

Next Steps

You've got the setup blueprint. Getting domains configured, inboxes warmed, and sequences running still takes 3 to 4 weeks of careful execution. If you'd rather skip the build and hand it off to a team that's run this stack across 3,000+ campaigns, that's what Modern Inbound does. Talk to us about your outbound setup.

How to integrate Inframail with Instantly in 2026