How Apollo + ColdRelay Work Together
ColdRelay (Infrastructure)
ColdRelay provides the mailboxes Apollo sends from. Each mailbox is a Microsoft 365 account on a dedicated, isolated Azure tenant with its own dedicated IP, fully-automated DNS (SPF, DKIM, DMARC), and a 95% inbox-placement guarantee. ColdRelay's pricing is per-mailbox: $1 (1-199), $0.85 (200-999), $0.70 (1K-4,999), $0.55 (5K+). Setup completes in 60 minutes, no warmup wait.
Apollo (Sending Platform)
Apollo.io is a sales intelligence and engagement platform — it bundles a B2B contact database (300M+ contacts), prospect filtering, multi-step sequences, dialer, deal management, and basic analytics into one workspace. The email-sending side is one component, not the whole product: Apollo's value-add is the integrated contact data + outreach orchestration, not the underlying mail transport. Apollo sends through whatever email account you connect to it.
Why use them together
Apollo is the prospecting and sequencing brain (database, filters, sequences, dialer). ColdRelay is the sending body (mailboxes, IPs, DNS). The combination gives you Apollo's contact-data advantage without burning your primary domain. Apollo's database surfaces the prospects; ColdRelay's isolated mailboxes deliver to them. If you ever switch sequencing tools, the ColdRelay mailboxes still work — they speak SMTP/IMAP and M365 OAuth like any standard infrastructure.
Connect Apollo to ColdRelay (Step-by-Step)
- 1
Order ColdRelay mailboxes
Sign up at coldrelay.com/sign-up, pick a domain (ColdRelay handles registration for $14), and order your mailbox count. The minimum is 50 mailboxes ($50/month at the base tier). ColdRelay's automation provisions the dedicated mail server, registers the domain, and creates all mailboxes inside an isolated Azure tenant.
Note: Provisioning takes 60 minutes end-to-end. You'll receive a CSV with every mailbox's SMTP host, port, username, and password — plus the option to connect via M365 OAuth for Apollo's native flow.
- 2
Wait for DNS propagation
ColdRelay configures SPF, DKIM, and DMARC records automatically on the new domain. DNS propagation usually completes in under an hour but can take up to 24. Verify with the Email Deliverability Test at coldrelay.com/tools/email-deliverability-test — when SPF, DKIM, DMARC, and MX all show as configured, you're ready to connect to Apollo.
Note: Don't start sending before all four records (SPF, DKIM, DMARC, MX) verify correctly. Sending before authentication is in place causes immediate spam-folder placement, and Apollo will flag the mailbox as unhealthy.
- 3
Connect mailboxes to Apollo
In Apollo, go to Settings → Mailboxes → Link Mailbox. You'll see three options: Google (OAuth), Microsoft (OAuth), and Custom SMTP/IMAP. For ColdRelay mailboxes, choose Microsoft and complete the OAuth handshake with the ColdRelay-provisioned credentials. Apollo redirects to the Microsoft consent screen, you approve, and the mailbox links in under 30 seconds.
Note: If your security policy blocks third-party OAuth grants in your Azure tenant, fall back to Custom SMTP/IMAP. Use the SMTP host (box.YOURDOMAIN.com), port 587, your full email as the username, the password from the ColdRelay CSV, and matching IMAP credentials on port 993.
- 4
Set daily limits per mailbox
In each Apollo mailbox's settings, set the daily send limit to 2 outbound emails per day (Apollo calls this the 'Daily Sending Limit' under Mailbox Health). This matches ColdRelay's per-mailbox cap. With 50 mailboxes you can send 100 outbound emails/day; 200 mailboxes = 400/day; 1,000 mailboxes = 2,000/day.
Note: Apollo's default daily limit is much higher (often 100+/mailbox). You MUST lower it to 2/day on ColdRelay mailboxes. Going higher is the single fastest way to degrade deliverability and voids ColdRelay's 95% inbox guarantee.
- 5
Configure warmup
Apollo has built-in warmup but it's less central than Instantly's or Smartlead's — Apollo's warmup network is smaller and the feature is positioned as a mailbox-health helper, not a core product pillar. Turn it on with a daily cap of 2 emails/mailbox. If you want a more aggressive warmup network, you can run a separate warmup service (Mailreach, Warmup Inbox) alongside Apollo using the same SMTP/IMAP credentials.
Note: ColdRelay mailboxes ship reputation-ready (the Azure tenant + dedicated IP isolation gives you a clean start), but 2 weeks of warmup at 2 emails/day is still recommended before scaling to full sending.
- 6
Build a sequence and prospect list
In Apollo, use the Search panel to filter the database for your ICP — title, company size, industry, location, technographics. Save the list, then create a sequence: subject lines, email bodies, follow-up cadence, and any voice/LinkedIn touchpoints. Assign your ColdRelay mailboxes as the sending accounts. Apollo distributes sends across all assigned mailboxes respecting each one's daily cap.
Note: Apollo's email-finder enriches contacts on-demand. Verify emails before adding to a sequence (Apollo's built-in verifier or ZenVerifier) — sending to invalid addresses tanks deliverability faster than anything else.
- 7
Enable reply detection and unsubscribe handling
In Apollo's sequence settings, enable 'Stop on Reply' and 'Stop on Auto-Reply' so a prospect who responds drops out of the cadence. Configure the unsubscribe link in the email template — Apollo can auto-append a one-click unsubscribe footer, which is required for CAN-SPAM compliance. ColdRelay mailboxes route replies through standard IMAP, so Apollo's reply detection works without special config.
Note: Use the CAN-SPAM Checker at coldrelay.com/tools/can-spam-checker to validate your template before launching a sequence.
- 8
Monitor mailbox health and deliverability
Apollo's Mailbox Health dashboard shows daily sent counts, bounce rate, reply rate, and Apollo's own health score per mailbox. Cross-check weekly with the Email Deliverability Test (SPF/DKIM/DMARC) and Google Postmaster Tools (spam rate, IP reputation). ColdRelay automatically monitors blocklists — you'll get an alert if any of your dedicated IPs hit a major blocklist (Spamhaus, Barracuda, SORBS, SpamCop).
Note: If Apollo flags a mailbox as 'Unhealthy', pause that mailbox immediately and investigate. The most common cause is exceeding the 2/day cap — Apollo's defaults will quietly push higher than you set if you don't recheck the limit after provisioning new mailboxes.
Key Considerations for Apollo + ColdRelay
Daily send limits per mailbox
Set Apollo's per-mailbox daily limit to 2 outbound + 2 warmup = 4 total/day MAX. Apollo's defaults are 100+/day, which is appropriate for a sales rep's primary inbox but catastrophic for cold-email-dedicated mailboxes. Scale total volume by adding more ColdRelay mailboxes, not by pushing existing ones harder.
Apollo is a database + engagement combo, not pure sending
Unlike Instantly or Smartlead (which are sending-first platforms), Apollo's biggest value-add is the integrated contact database. You're paying Apollo for prospect data and sequence orchestration; ColdRelay handles the actual mail transport. This separation is healthy — you can switch sequencing tools later without losing your infrastructure investment, and you can swap data sources without rebuilding mailboxes.
M365 OAuth path is the cleanest connection
Apollo's Microsoft OAuth flow works directly with ColdRelay's M365 mailboxes — no SMTP/IMAP credentials to copy-paste, no app-password steps, no token-refresh headaches. The OAuth handshake completes inside Apollo's UI. If your tenant policy blocks third-party OAuth, fall back to Custom SMTP/IMAP with the credentials from the ColdRelay CSV.
Dedicated IPs end shared-IP risk
Each ColdRelay mailbox is on a dedicated IP within your isolated Azure tenant. Apollo doesn't provide infrastructure, so without ColdRelay you're typically sending from Google Workspace or Microsoft 365 shared infrastructure where bad actors on the same IP damage everyone's deliverability. With ColdRelay your IP reputation is entirely your own.
Apollo's built-in warmup is lighter than Instantly's
Apollo includes warmup but it's a smaller, less-emphasized feature than Instantly's or Smartlead's warmup networks. For best reputation-building, consider running a dedicated warmup tool (Mailreach, Warmup Inbox) alongside Apollo on the same mailboxes. ColdRelay mailboxes accept multiple simultaneous SMTP/IMAP connections cleanly.
Domain-rotation strategy
ColdRelay caps each domain at 100-150 mailboxes for deliverability reasons. If you need 500+ mailboxes, you'll order multiple domains. Apollo handles multi-domain campaigns — assign mailboxes from each domain to different sequences or sub-segments to spread risk across domains.
Pricing Snapshot
ColdRelay
ColdRelay's per-mailbox cost ranges from $1.00 (1-199 mailboxes) down to $0.55 (5,000+). Domain registration is $14/year, one-time. For 200 mailboxes: 200 × $0.85 = $170/month + $14 annual domain cost.
Apollo
Apollo's pricing is per-seat. Free plan covers limited credits and basic features. Basic is ~$49/user/month, Professional ~$79/user/month, Organization ~$119/user/month (annual billing). Pricing scales with seats and credit allocation (contact reveals, email finds), not with mailbox count — you can connect multiple mailboxes per seat at no extra Apollo cost.
Total monthly
A typical 200-mailbox cold email operation with one Apollo seat: ColdRelay infrastructure at ~$170/month + Apollo Professional at $79/month = ~$249/month total. At 1,000 mailboxes with 3 Apollo seats: ColdRelay $700/month + Apollo Organization 3-seat at ~$357/month = ~$1,057/month. Compare against Google Workspace at $6+/mailbox/month: 200 GW mailboxes alone would be $1,200/month before Apollo's seat cost.
Common Issues + Fixes
⚠ Microsoft OAuth handshake fails with 'consent not granted' error
Your Azure tenant admin (in this case, the isolated ColdRelay tenant) needs to allow third-party OAuth grants for Apollo. ColdRelay's tenant config allows this by default, but if you've hardened the tenant, re-enable third-party app consent under Azure AD → Enterprise Applications → Consent and permissions. Alternatively, fall back to Custom SMTP/IMAP — same mailbox, no OAuth required.
⚠ Apollo's Mailbox Health dashboard shows mailboxes as 'Unhealthy'
Check the daily send count first — Apollo often resets its internal cap to its default (100+/day) after a mailbox reconnect. Re-set the Daily Sending Limit to 2. Next, run the Email Deliverability Test to confirm SPF/DKIM/DMARC still pass. If health stays poor despite a 2/day cap and clean DNS, the issue is usually campaign content — check the CAN-SPAM Checker and review subject lines.
⚠ Emails landing in spam at Gmail despite clean ColdRelay setup
Run the Email Deliverability Test against the domain. If SPF, DKIM, or DMARC fails, records may not have propagated yet — wait 24 hours. If they all pass, check Google Postmaster Tools. The most common post-authentication spam cause is Apollo's default high send limit silently re-applying after a sequence launch — verify the per-mailbox cap is still 2/day.
⚠ Apollo's unified inbox shows no replies even though prospects are replying
If you connected via M365 OAuth, replies surface natively through Microsoft Graph and should appear within a minute. If you connected via Custom SMTP/IMAP, Apollo polls IMAP on port 993 with TLS — verify the IMAP credentials match the ColdRelay CSV. Test connection in Apollo's mailbox settings (Test Connection button). Most commonly the IMAP password drifted after a mailbox reset.
⚠ Bounce rate spiking after Apollo email-finder enrichment
Apollo's email-finder isn't 100% accurate — enrichments include some guess-pattern emails that will bounce. Always verify the list before sending: use Apollo's built-in verifier or pipe the list through ZenVerifier first. A bounce rate above 5% on a fresh ColdRelay mailbox will damage its reputation fast and trigger Apollo's Unhealthy flag.
Frequently Asked Questions
Do I need ColdRelay if I already have Apollo?
Apollo is a sales intelligence and sequencing platform — it provides the contact database, prospect filtering, and sequence orchestration, but not the email infrastructure. Apollo sends through whatever mailbox you connect to it (Google Workspace, M365, or custom SMTP). ColdRelay provides those mailboxes purpose-built for cold email at $0.55-$1.00/mailbox/month, dramatically cheaper than Google Workspace ($6+/mailbox/month) and with better isolation than shared infrastructure.
Is ColdRelay better than Google Workspace for use with Apollo?
For cold email at any scale beyond a handful of mailboxes: yes. Google Workspace charges $6+/mailbox/month and shares some risk across all GW senders. ColdRelay charges $0.55-$1.00/mailbox/month, gives each customer a dedicated Azure tenant with dedicated IPs, and bakes SPF/DKIM/DMARC automation into provisioning. Apollo connects to both equally well via M365 OAuth or SMTP/IMAP — the question is just infrastructure cost and isolation.
Should I use M365 OAuth or Custom SMTP/IMAP to connect ColdRelay to Apollo?
M365 OAuth is cleaner — no credentials to paste, no token-refresh issues, and reply syncing happens through Microsoft Graph. Use OAuth as the default. Fall back to Custom SMTP/IMAP only if your tenant policy blocks third-party OAuth grants, or if you have a specific reason to keep auth out-of-band. Both connect to the same ColdRelay mailbox and have identical send capabilities.
How many mailboxes do I need for my Apollo sequences?
ColdRelay's per-mailbox cap is 2 outbound emails/day for optimal deliverability. If your Apollo sequence sends 1,000 emails/day, you need 500 mailboxes. The Mailbox Calculator at coldrelay.com/tools/mailbox-calculator lets you input your target daily volume and gives you the exact mailbox count + pricing tier. Apollo doesn't cap how many mailboxes you can connect per seat — only the seat itself is metered.
Will Apollo's built-in warmup be enough for ColdRelay mailboxes?
Apollo's warmup is smaller and less emphasized than Instantly's or Smartlead's networks. For most users it's sufficient as a baseline, especially since ColdRelay mailboxes ship reputation-ready on isolated IPs. If you want more aggressive warmup, run a dedicated tool (Mailreach, Warmup Inbox) alongside Apollo on the same mailboxes — they don't conflict.
Can I switch from Apollo to Instantly or Smartlead later without losing my ColdRelay setup?
Yes. ColdRelay mailboxes are vendor-neutral — they speak SMTP/IMAP and M365 OAuth like any standard infrastructure. If you decide Apollo's database isn't worth the price or you prefer a sending-first platform, you can disconnect from Apollo and reconnect the same mailboxes to Instantly, Smartlead, or any other tool that supports custom SMTP/IMAP. The infrastructure investment carries over.
What if Apollo's deliverability is bad with my ColdRelay mailboxes?
That's almost always one of three things: (1) Apollo's default daily cap silently re-applied above 2/day, (2) Apollo's email-finder enriched contacts with guess-pattern emails that bounce, or (3) campaign content triggering spam filters. ColdRelay's 95% inbox guarantee means the infrastructure is doing its job. Verify the cap, run new lists through verification, and use the CAN-SPAM Checker before assuming the issue is infrastructure.