How Salesloft + ColdRelay Work Together
ColdRelay (Infrastructure)
ColdRelay provisions the mailboxes Salesloft 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. Pricing is per-mailbox: $1.00 (1-199), $0.85 (200-999), $0.70 (1K-4,999), $0.55 (5K+). 50-mailbox minimum order. Setup completes in 60 minutes.
Salesloft (Sending Platform)
Salesloft is an enterprise sales engagement platform — really a revenue orchestration suite covering cadences (sequenced multi-touch outbound), an integrated dialer, conversation intelligence, and deal management. It's the system reps live in, with deep Salesforce/HubSpot CRM sync and pipeline analytics. Salesloft does NOT provision mailboxes or own the underlying email infrastructure — reps connect their own work mailbox (Google Workspace or Microsoft 365) and Salesloft sends through it.
Why use them together
Salesloft handles the sales-team-facing layer (cadences, dialer, CRM sync, rep coaching). ColdRelay handles the deliverability-facing layer (mailbox provisioning, dedicated IPs, DNS authentication). The pairing is most useful for outbound-heavy teams that want enterprise sales-engagement tooling without binding their primary corporate mailboxes — and any team building outbound at scale rather than from individual reps' personal inboxes.
Connect Salesloft to ColdRelay (Step-by-Step)
- 1
Confirm Salesloft will accept external M365 tenants
Before ordering mailboxes, check with your Salesloft account team that your contract permits connecting external Microsoft 365 tenants (the ColdRelay mailboxes will live in an Azure tenant separate from your corporate M365). Salesloft's primary mailbox auth is OAuth against the tenant the user logs in from, and some enterprise contracts restrict which tenants are permitted. Confirm before you provision.
Note: If your Salesloft contract only allows your corporate M365 tenant, the SMTP-relay path in step 3 is the alternative — but custom SMTP is an enterprise-only feature at Salesloft and requires explicit account-team enablement.
- 2
Order ColdRelay mailboxes
Sign up at coldrelay.com/sign-up, pick a sending domain (ColdRelay handles registration for $14/year if you need a new one), and order your mailbox count. The minimum order is 50 mailboxes ($50/month at the base tier). ColdRelay's automation provisions the dedicated mail server, registers the domain, configures DNS, and creates each mailbox inside an isolated Azure tenant.
Note: Provisioning takes 60 minutes end-to-end. You'll receive a CSV listing every mailbox's SMTP host, port, username, and password once it completes — and each mailbox will also have M365 web credentials usable for OAuth flows.
- 3
Decide your connection path: OAuth vs SMTP relay
Salesloft supports two mailbox connection patterns. Path A (OAuth, default): each ColdRelay mailbox connects via Salesloft's Microsoft 365 OAuth flow — the rep signs in with the mailbox's M365 credentials and Salesloft requests Mail.Send/Mail.Read scopes. Works only if Salesloft is configured to accept your ColdRelay Azure tenant. Path B (SMTP relay, enterprise-only): your Salesloft customer success manager enables the custom-SMTP feature on your workspace; you then add each mailbox by its SMTP host (box.YOURDOMAIN.com), port 587, and the password from the ColdRelay CSV.
Note: Path A is faster to set up but requires Salesloft to permit external M365 tenants. Path B works regardless of tenant policy but is gated behind enterprise pricing and an account-team enablement ticket — expect 1-2 weeks of back-and-forth before the feature flag flips.
- 4
Wait for DNS to fully propagate
ColdRelay configures SPF, DKIM, and DMARC records automatically on the new domain. Propagation usually completes within 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, the domain is safe to send from.
Note: Do not start any Salesloft cadence before SPF/DKIM/DMARC verify. Sending before authentication is in place causes immediate spam-folder placement and can damage IP reputation in the first 48 hours, before warmup has built any positive signal.
- 5
Connect mailboxes inside Salesloft
In Salesloft, go to Settings → Email → Email Accounts → Connect an Email Account. For Path A, choose Microsoft 365 and sign in with each ColdRelay mailbox's credentials. For Path B (if enabled), choose Custom SMTP and paste host (box.YOURDOMAIN.com), port 587, the username (full email address), and the password from the CSV. Repeat per mailbox. Salesloft tests each connection and marks the account Active once it validates.
Note: Salesloft's OAuth grant prompt will show the requested permissions — Mail.Send, Mail.Read, offline_access. The first mailbox connection in a new tenant may require an admin consent prompt. ColdRelay tenants are pre-configured to grant this without manual approval.
- 6
Set daily send limits per mailbox in Salesloft
In Salesloft, set each mailbox's daily send limit to 2 outbound emails per day. Salesloft's UI usually defaults to much higher numbers (50, 100, even 250) appropriate for warm corporate mailboxes — these defaults will torch a cold-outbound mailbox in a week. With 50 ColdRelay mailboxes you can send 100 cold emails/day; 200 mailboxes = 400/day; 1,000 mailboxes = 2,000/day. Pair this with warmup running at 2 emails/day for the first 14 days of any new mailbox.
Note: Going above 2/day/mailbox is the single fastest way to degrade ColdRelay deliverability. ColdRelay's pricing model assumes 2/day — scale total volume by adding more mailboxes, not by pushing existing ones harder. The 2 outbound + 2 warmup = 4/day cap is non-negotiable for the 95% inbox guarantee.
- 7
Configure your first cadence
In Salesloft, create a cadence (the sequence of touchpoints), assign your prospect list, write the email steps with personalization tokens, and assign your ColdRelay mailboxes as the sending accounts. Salesloft distributes sends across all assigned mailboxes respecting each one's daily cap. Hook up Salesforce/HubSpot sync if you want prospect-status changes reflected in CRM automatically.
Note: Use Salesloft's Snippets and Dynamic Tags for personalization. Avoid identical subject lines across the cadence — generate variations with the Spintax Generator at coldrelay.com/tools/spintax-generator and paste them as Salesloft template variants.
- 8
Monitor deliverability ongoing
Run the Email Deliverability Test weekly to verify SPF/DKIM/DMARC stay passing. Check Salesloft's per-mailbox health dashboard (Settings → Email Accounts → individual mailbox → Health) — bounce rate, reply rate, and disconnection events surface there first. ColdRelay separately monitors major blocklists (Spamhaus, Barracuda, SORBS, SpamCop) and alerts you if any dedicated IP hits one.
Note: The 95% inbox-placement guarantee is contingent on holding the 2-outbound + 2-warmup cap. Exceeding it voids the guarantee. If you see Salesloft's per-mailbox reply rate dropping below 1% for 7 consecutive days, run a content audit before assuming infrastructure.
Key Considerations for Salesloft + ColdRelay
Daily send limits are the single most important setting
Set Salesloft's per-mailbox daily limit to 2 outbound + 2 warmup = 4 total/day MAX. Salesloft's UI defaults are tuned for warm corporate mailboxes sending to existing customers, not cold outbound. Reps used to Salesloft's higher defaults often want to push the limit — push back. Scaling volume happens by adding mailboxes, not by raising per-mailbox caps.
OAuth vs SMTP-relay path constraint
Salesloft's default mailbox auth is OAuth against Google Workspace or Microsoft 365. ColdRelay mailboxes are M365 accounts in an isolated Azure tenant — they CAN connect via Salesloft's M365 OAuth if your Salesloft contract permits external M365 tenants. If it doesn't, the SMTP-relay path exists but is enterprise-only and requires account-team enablement. Confirm your contract before ordering mailboxes.
Dedicated IPs vs shared deliverability risk
Each ColdRelay mailbox is on a dedicated IP within your isolated Azure tenant. Compare this to running Salesloft on corporate Google Workspace mailboxes — those sit on shared sending infrastructure where IP reputation is pooled across many senders. With ColdRelay your IP reputation is yours alone, which matters most when you're sending from a domain that's never sent cold email before.
CRM sync still works through ColdRelay mailboxes
Salesloft's Salesforce and HubSpot sync operates on the cadence-and-prospect layer, not the mailbox layer. Replies received on ColdRelay mailboxes flow through Salesloft's normal email-tracking pipeline and update CRM records as expected. No special configuration needed — the mailbox is just a transport.
Separating cold from warm outbound
Many Salesloft customers run their cold outbound through ColdRelay mailboxes on a separate sending domain (e.g., outreach.yourcompany.io rather than yourcompany.com), and keep warm outbound — replies to existing customers, post-meeting follow-ups, scheduling — on their primary corporate mailboxes. This protects the primary domain's deliverability from any cold-outbound mistakes.
Switching cost is low
If your team decides Salesloft isn't the right engagement layer and wants to switch to Outreach, Reply, or another platform, your ColdRelay mailboxes work with any platform supporting M365 OAuth or custom SMTP. The infrastructure investment carries forward — only the sales-engagement layer changes.
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 a 200-mailbox setup: 200 × $0.85 = $170/month plus the $14 annual domain cost.
Salesloft
Salesloft pricing is enterprise / by-quote and not published publicly — you'll negotiate per seat with their sales team, typically in the range of mid-3-figures to low-4-figures per rep per year depending on tier (Essentials, Advanced, Premier) and add-ons (dialer, conversation intelligence, deal management). For exact current pricing see salesloft.com/pricing.
Total monthly
Because Salesloft prices per seat (rep) and ColdRelay prices per mailbox, a typical 10-rep team with 200 cold mailboxes might look like: ColdRelay at ~$170/month + Salesloft for 10 reps at negotiated rate. The infrastructure cost stays predictable as you add reps; only the sales-engagement layer scales with headcount. Compare against running 200 Google Workspace mailboxes at $6+ each = $1,200/month for mailboxes alone, before Salesloft seats.
Common Issues + Fixes
⚠ Salesloft rejects the ColdRelay mailbox during M365 OAuth: 'tenant not permitted'
Your Salesloft workspace is configured to allow only your corporate M365 tenant. Either contact your Salesloft account team to whitelist the ColdRelay tenant (provide them the tenant ID from your ColdRelay dashboard) or switch to the custom-SMTP path if your contract includes it. The whitelist request is a standard ticket but can take 5-10 business days.
⚠ Mailbox connects but Salesloft shows 'Authentication Required' the next day
Salesloft's OAuth refresh-token flow occasionally fails when an M365 mailbox's password was rotated. Confirm in your ColdRelay dashboard that the mailbox's M365 password hasn't changed, then in Salesloft go to Email Accounts → the affected mailbox → Reconnect. If the issue repeats across multiple mailboxes, check whether your Azure tenant's conditional access policies are forcing reauth at a shorter interval than Salesloft's refresh cadence.
⚠ Emails landing in spam at Gmail despite SPF/DKIM/DMARC passing
Run the Email Deliverability Test against the domain to confirm authentication. If all four (SPF, DKIM, DMARC, MX) pass, the issue is almost always either (a) exceeding 2/day/mailbox in Salesloft cadences, or (b) cadence content triggering spam filters — heavy link density, suspicious unsubscribe wording, or sender display name mismatch. Check the CAN-SPAM Checker at coldrelay.com/tools/can-spam-checker and the Spam Words Checker.
⚠ Salesloft per-mailbox health dashboard shows bounce rate climbing above 5%
Bounce-rate spikes are almost always a list-hygiene problem, not infrastructure. Pause the cadence, run the affected prospect list through email verification (ColdRelay's sister product ZenVerifier or any reputable verifier), remove invalid and catch-all addresses, then resume. ColdRelay's 95% inbox guarantee assumes a verified list — sending to an unverified list voids it because the bounces themselves damage IP reputation.
⚠ Custom SMTP path enabled but Salesloft rejects credentials with 'authentication failed'
Three things to check. (1) Confirm you're using the SMTP password from the ColdRelay CSV, not the M365 web-login password — they're separate for some mailbox configurations. (2) Verify SMTP host is box.YOURDOMAIN.com (not mail. or smtp.) and port 587 with STARTTLS. (3) If recently provisioned, the mailbox may not have finished initialization — wait 30 minutes after provisioning completes before connecting in Salesloft.
Frequently Asked Questions
Do I need ColdRelay if my team already uses Salesloft on corporate Google Workspace?
If your team is sending warm outbound only — replies, follow-ups, post-meeting notes — corporate Google Workspace is fine. If you're running any cold outbound through Salesloft (cadences to prospects who haven't engaged before), running it through your primary corporate mailboxes puts your main domain's deliverability at risk. ColdRelay separates that risk: cold outbound flows through dedicated mailboxes on a separate sending domain, while corporate mailboxes stay clean.
Will ColdRelay mailboxes actually connect to Salesloft, or is the OAuth path blocked?
It depends on your Salesloft contract. By default Salesloft's M365 OAuth flow accepts any M365 tenant, and ColdRelay mailboxes are standard M365 accounts in an isolated Azure tenant — so they connect normally. However, some enterprise Salesloft contracts restrict the flow to a specific corporate tenant. Confirm with your Salesloft account team before ordering. If your contract restricts external tenants, the custom-SMTP path is the alternative but is enterprise-only and requires account-team enablement.
How many ColdRelay mailboxes do I need for my Salesloft cadences?
ColdRelay's per-mailbox cap is 2 outbound emails/day for optimal deliverability. So if your team wants to send 1,000 cold emails/day across cadences, you need 500 mailboxes. The Mailbox Calculator at coldrelay.com/tools/mailbox-calculator translates target volume into mailbox count and pricing tier. Remember to also account for warmup running in parallel — the practical max per mailbox is 4 total/day (2 outbound + 2 warmup).
Does ColdRelay charge per rep like Salesloft does?
No. ColdRelay charges per mailbox per month, completely independent of seat count. A 5-rep team and a 50-rep team running the same number of cold mailboxes pay ColdRelay the same. This is by design — infrastructure cost should scale with sending volume, not headcount. Salesloft handles the per-rep layer; ColdRelay handles the per-mailbox layer.
Can replies received on ColdRelay mailboxes update Salesforce automatically through Salesloft?
Yes. Salesloft's CRM sync operates on cadences and prospect interactions, not at the mailbox-protocol layer. Replies received on any connected mailbox — corporate or ColdRelay — flow through Salesloft's normal email-tracking pipeline and update Salesforce/HubSpot records as configured. The mailbox is just a transport from Salesforce's perspective.
Is the Salesloft + ColdRelay combination overkill for a 2-3 person startup?
Probably yes. Salesloft's pricing model and feature depth are tuned for sales teams with 10+ reps, structured cadences, and CRM-driven workflows. For a 2-3 person startup doing founder-led outbound, a lighter sender like Instantly or Smartlead paired with ColdRelay infrastructure usually delivers more for less spend. Revisit Salesloft when you've hired a dedicated SDR team.
What if a ColdRelay mailbox gets suspended by Microsoft inside the Azure tenant?
Rare but possible if the cadence is aggressive enough to trigger Microsoft's outbound abuse detection. ColdRelay's monitoring catches suspension events typically within hours and either auto-restores the mailbox or replaces it with a fresh one at no additional cost. The reason these are rare on ColdRelay specifically: the per-tenant isolation means abuse signals from one customer can't cross-contaminate another's reputation, and the 2/day cap stays well below Microsoft's outbound thresholds.