StackMail vs Apollo: 2026 Side-by-Side Comparison
Last updated: 2026-05-04 - written and reviewed by the StackMail team. We are a competing provider; this comparison is honest about both products. Verify pricing on Apollo before purchase as plans change.
The short answer
Apollo is a prospecting and sequencing platform with around 270 million B2B contacts in its database, used by 600,000+ companies. StackMail is mailbox infrastructure that costs $2.50 per Google Workspace or Microsoft 365 mailbox. We are not Apollo's competitor - we are the layer underneath Apollo's sequencer. If you searched "Apollo alternative" because you want a different lead database, look at ZoomInfo, Lusha, or Clay. If you want a different sequencer, look at Instantly, Smartlead, Saleshandy, or Lemlist. If you want better mailboxes underneath whichever sequencer you keep using, that is what StackMail does.
Our verdict
Apollo and StackMail are complements, not competitors. The cleanest cold email stack in 2026 is Apollo for the lead database (because nobody else gives you 270M contacts at Apollo's price point), the sequencer of your choice for sending (Apollo's own, Instantly, Smartlead, Saleshandy, or Lemlist), and StackMail for mailbox infrastructure (because the mailbox layer is its own discipline and bundling it into a sequencer or a CRM is what causes deliverability problems at scale). Pick Apollo if you need a lead database and a starter sequencer in one tool. Add StackMail underneath when your campaigns scale past 30 mailboxes and you need real Google Workspace or Microsoft 365 seats with isolated tenants, automated SPF/DKIM/DMARC, and the freedom to swap sequencers without re-warming. Replace Apollo with something else only if the lead database is no longer worth the per-seat cost - and even then, StackMail is not what replaces it.
Why people search for Apollo alternatives
If you searched "Apollo alternative" and landed on a mailbox infrastructure page, we owe you the most honest paragraph on this site. Apollo is not a mailbox provider. Apollo is a sales engagement platform with a lead database of roughly 270 million B2B contacts, a sequencer for outbound campaigns, a dialer for outbound calls, deal management, and analytics. Around 600,000 companies use it. StackMail is the cheap, reliable mailbox layer that lives underneath whatever sequencer you choose. The two products solve different problems and the rest of this page is going to spell out exactly what you probably wanted when you searched - and where StackMail fits, if at all.
There are three distinct things people mean when they type "Apollo alternative" into Google. First: I want a different B2B contact database because Apollo's data quality dropped, my territory is undercovered, or my budget shrank. The honest answer there is ZoomInfo at the high end, Lusha or Cognism in the mid-market, and Clay or Apollo competitors like RocketReach or LeadIQ on the lighter end. StackMail does not have a contact database and we are not building one. Second: I want a different sequencer because Apollo's sending side feels like a bolt-on, deliverability is uneven, or my agency runs multi-tool stacks. The honest answer there is Instantly, Smartlead, Saleshandy, Lemlist, Reply, Outreach, or Salesloft depending on your scale and use case. We have written deep comparison pages for several of these. Third: I am running campaigns through Apollo and my mailboxes are the bottleneck - either I am using Apollo's connection to my single Gmail account and getting deliverability issues, or I tried to add Google Workspace seats and discovered the SPF/DKIM/DMARC and tenant-isolation work is non-trivial. That third profile is the only one StackMail solves for, and we solve it well.
We respect Apollo as a category-defining product. The combination of a 270M contact database, a workable sequencer, a dialer, and a deal pipeline at $49 to $119 per user per month is genuinely strong economics for a small sales team. Apollo's compliance posture (SOC 2, ISO 27001, GDPR, PCI, CCPA) is enterprise-grade. Their HubSpot-style inbound brand is the strongest in the cold email category. We are not going to write a hit piece. We are going to clarify the three buckets above, recommend honestly within each one, and explain why - if you keep Apollo - StackMail belongs in your stack as the mailbox layer underneath.
Apollo vs StackMail: Feature comparison
Side-by-side on the features that matter for cold email infrastructure: mailbox provider, DNS automation, warmup, sequencer integrations, monitoring, support, and pricing.
| Feature | Apollo | StackMail |
|---|---|---|
| B2B contact database (~270M) | Yes | No |
| Built-in sequencer | Yes | No |
| Dialer / outbound calling | Yes | No |
| Deal management / CRM-lite | Yes | No |
| Email finder / verifier | Yes | Free verifier in /tools |
| Provisions Google Workspace mailboxes | No | Yes |
| Provisions Microsoft 365 mailboxes | No | Yes |
| Automated SPF / DKIM / DMARC setup | No | Yes |
| Tenant isolation per workspace | No | Yes |
| Pre-warmed mailboxes on delivery | No | Yes |
| Direct admin-console access to mailboxes | N/A (does not own them) | Yes |
| Connects to Smartlead / Instantly / Saleshandy | N/A | Yes |
| SOC 2 / ISO 27001 / GDPR / PCI / CCPA badges | Yes | GDPR + Google/Microsoft compliance perimeter |
| Pricing model | $49-$119 per user/month | $2.50 per mailbox/month |
| Free tier | Yes | Free tools, paid mailboxes |
| Best for prospecting | Yes | No |
| Best for mailbox infrastructure | No | Yes |
Pricing breakdown at scale
Per-mailbox cost matters most when you scale past 30 mailboxes. Here is what a 10, 30, 100, and 300 mailbox setup costs on Apollo versus StackMail (annual billing where available).
| Tier | Mailboxes | Apollo / month | Per mailbox | StackMail / mailbox |
|---|---|---|---|---|
| Free | 0 | $0 | $0.00 | $2.50 (annual) |
| Basic | 0 | $49 | $0.00 | $2.50 (annual) |
| Professional | 0 | $79 | $0.00 | $2.50 (annual) |
| Organization | 0 | $119 | $0.00 | $2.50 (annual) |
Limited credits, basic sequencer, BYO mailbox. Per user per month. Not a mailbox plan - Apollo does not sell mailboxes.
Where Apollo genuinely wins
We will not pretend StackMail wins on every dimension. Apollo has real advantages worth naming.
- Lead database breadth and price. Roughly 270 million B2B contacts at $49-$119 per user per month is genuinely the best price-per-contact in the category. ZoomInfo has comparable depth but charges 5-10x more on enterprise contracts. Lusha and Cognism are cheaper per seat but smaller in coverage, particularly in long-tail industries. If your team's bottleneck is finding contacts, Apollo is hard to beat economically.
- Unified prospecting plus sequencing in one tool. For a single-rep founder or a 5-person sales team, the workflow of searching contacts, building a list, and dropping them into a sequence without leaving the tool is genuinely lower-friction than a multi-tool stack. The integration tax of Clay-plus-Smartlead-plus-CRM is real and Apollo eliminates it for the small-team case.
- Enterprise compliance. SOC 2, ISO 27001, GDPR, PCI, and CCPA badges in writing. For procurement-heavy buyers in regulated industries, Apollo passes the security review faster than smaller specialized tools that are still building toward those certifications. StackMail is GDPR-compliant and we operate inside the Google Workspace and Microsoft 365 compliance perimeters but we do not have Apollo's badge collection on our own corporate envelope.
- Inbound brand and content moat. Apollo's blog, sales academy, and template library are the closest thing the cold email category has to HubSpot's content empire. They rank on category-defining queries and that drives organic signups at a velocity smaller competitors cannot match. If you are evaluating Apollo because you have read fifteen of their posts, that is the funnel working as designed.
- Polished UX. The dashboard is fast, the search filters are deep, the sequence builder is competent, and the integrations into HubSpot, Salesforce, and the major CRMs are first-party. New users hit a clean experience and the time-to-first-value is short.
- Free tier. Apollo's $0 plan gets a curious user into the product without a credit card. That is genuinely useful for evaluation and is rarer than it should be in this category.
Where Apollo falls short
The reasons people search for "Apollo alternatives." If any of these matter to you, StackMail is the cheaper drop-in.
- Mailbox layer is BYO and thin. Apollo connects to your Gmail or Outlook account and sends through that. There is no built-in mailbox provisioning, no automated SPF/DKIM/DMARC, no tenant isolation, and no warmup pool you control. If you scale past one or two personal mailboxes, you are on your own to provision Google Workspace or Microsoft 365 seats, configure DNS, warm them up, and rotate them. Most teams discover this gap the painful way at the 30-mailbox mark when deliverability collapses.
- Per-seat pricing model. Apollo is priced per user per month, not per mailbox or per campaign. If you need a sales engagement platform, that math works. If you really only need the sequencer to run cold email from 50 mailboxes you provisioned elsewhere, you are still paying $79-$119 per user even though you only have one or two users actually using the platform. Specialized sequencers like Smartlead or Saleshandy price per mailbox or per inbox and come out cheaper for high-volume single-operator outbound.
- Deliverability ceiling. Apollo's sequencer works fine at modest volumes from one or two mailboxes, but the platform is not designed for the 50-300 mailbox cold email programs that agencies and growth teams run. You will hit issues with throttling, account-level reputation contagion, and lack of granular per-mailbox controls. Specialized cold email sequencers (Instantly, Smartlead, Saleshandy) have spent years on these specific edge cases.
- Data quality complaints. The flip side of having 270M contacts is that the bottom 30-40% of those contacts are stale, mis-titled, or wrong-company. Power users routinely report 20-30% bounce rates on raw Apollo lists without manual verification or a third-party verifier. ZoomInfo and Cognism have higher per-contact prices and meaningfully cleaner data; this is the trade-off.
- Lock-in to Apollo's database via the workflow. Once your sequence sources, contact ownership, and pipeline data live inside Apollo, switching to a multi-tool stack means rebuilding several workflows. Apollo benefits from this but it is a real cost to you if you ever want to optimize each layer independently.
- Not a mailbox provider. We listed this last because it is not really a flaw - Apollo never claimed to be a mailbox provider - but enough searchers arrive here confused that it is worth saying explicitly. Apollo does not provision mailboxes. Apollo does not configure DNS for you. Apollo does not run a warmup pool for newly-created mailboxes. If you want those things, you need a separate mailbox infrastructure provider and StackMail is one option in that category.
Stay with Apollo if
- Small sales teams that need a unified prospecting-plus-sequencing tool and only run modest outbound volume from a handful of mailboxes. Apollo's bundle math is unbeatable for this profile.
- Founders evaluating cold email for the first time who want to test the channel without buying four separate tools. Start on Apollo's free tier, run a few hundred sends, decide if outbound works for your motion, and only then invest in a specialized stack.
- Teams in regulated industries where the SOC 2 / ISO 27001 / GDPR / PCI / CCPA badge collection meaningfully shortens the procurement cycle.
- Anyone whose primary bottleneck is finding contacts rather than sending email. Apollo's database is the product; the sequencer is the bonus.
- Existing Apollo customers who are happy with the platform but discovering that mailbox provisioning is a separate problem - you do not need to leave Apollo, you just need to add a mailbox layer underneath. That is what StackMail does.
Switch to StackMail if
- If "switch" means leave Apollo entirely: agencies running 50-300+ mailboxes for clients where the per-seat pricing is uneconomical and where specialized sequencers (Smartlead, Saleshandy) plus a dedicated lead source (Clay, ZoomInfo, or LinkedIn Sales Navigator) plus mailbox infrastructure (StackMail) builds a cheaper, more flexible stack. That is a multi-tool migration, not a one-for-one swap.
- If "switch" means change the sequencer but keep the lead database: customers whose Apollo sequencer feels constraining at scale should evaluate Instantly, Smartlead, Saleshandy, or Lemlist as the sending layer. Apollo's database export plus a specialized sequencer plus StackMail mailboxes is a common upgrade path.
- If "switch" means change the lead database but keep the sequencer: customers whose Apollo data quality is hurting bounce rates and reply rates should evaluate ZoomInfo (premium), Lusha or Cognism (mid), or Clay (waterfall enrichment from multiple sources) as the prospecting layer.
- Anyone who needs proper mailbox infrastructure underneath their cold email program. This is not a switch - it is an addition. Keep whichever combination of lead database and sequencer works for your motion, and put StackMail mailboxes underneath.
- Solo operators who only need a sequencer (not a lead database) and find Apollo's per-seat pricing wasteful. Specialized sequencers price per mailbox or per inbox and come out 2-3x cheaper for the same outbound volume.
How to migrate from Apollo to StackMail (5 steps)
Practical migration playbook. Plan a 14-21 day overlap so new mailboxes warm up before you cut over - this is true regardless of which provider you switch to.
1. Decide what you actually want to migrate
Apollo is three products in a trench coat: lead database, sequencer, and CRM-lite. Before moving anything, write down which of those you actually use. If you only use the lead database, switching providers is a database swap (ZoomInfo, Lusha, Cognism, Clay) and StackMail is irrelevant. If you only use the sequencer, switching is a sequencer swap (Instantly, Smartlead, Saleshandy, Lemlist) and StackMail is the mailbox layer underneath. If you use all three, you are looking at a multi-tool migration plan, not a one-for-one replacement. The rest of these steps assume you are adding StackMail mailboxes underneath whatever sequencer you keep using - Apollo's own or a specialized one.
2. Audit your current sending setup
List every mailbox currently connected to Apollo's sequencer. Note which ones are personal Gmail accounts, which are Google Workspace seats on your primary domain, and which are dedicated cold email mailboxes on lookalike domains. The personal ones are the highest-risk for your primary domain reputation; those should move to StackMail-provisioned tenants on isolated lookalike domains as quickly as possible. Dedicated lookalike-domain mailboxes can stay on the original provider until rotation is convenient.
3. Provision StackMail mailboxes on isolated lookalike domains
Sign up at stackmail.io. Buy lookalike domains (e.g., yourcompany.io, getyourcompany.com, hi-yourcompany.com) inside StackMail or bring your own. Provisioning creates a Google Workspace or Microsoft 365 tenant per domain, configures SPF, DKIM, and DMARC automatically, creates the mailboxes, and starts warmup. Plan for 14-21 days of warmup before these mailboxes carry production cold email volume. This is true regardless of which mailbox provider you use - warmup pacing is dictated by Gmail and Outlook, not by us.
4. Connect StackMail mailboxes to Apollo (or to a different sequencer)
If you are keeping Apollo as the sequencer, add each StackMail mailbox to Apollo's mailbox connections page via OAuth. Apollo accepts standard Gmail and Outlook OAuth, which is what StackMail mailboxes are. If you are migrating off Apollo's sequencer entirely, point the StackMail mailboxes at Smartlead, Instantly, Saleshandy, or whichever sequencer you chose. The mailboxes themselves do not care which sequencer connects to them - they are real Google Workspace or Microsoft 365 seats and they speak standard OAuth + SMTP.
5. Migrate sequences and disconnect old mailboxes
Move active sequences to use the new StackMail mailbox pool. Let in-flight campaigns from the old mailboxes drain naturally - do not pull mid-campaign or you will burn the prospect relationship. Once new sequences are running cleanly through StackMail mailboxes for 14-21 days and warmup is complete, disconnect the old mailboxes from Apollo. If those old mailboxes were personal Gmail accounts, this is also when you should rotate any other workflows that lived in them. The result is Apollo (or another sequencer) on top, StackMail mailboxes underneath, and your primary domain insulated from cold email risk.
Frequently asked questions
Is StackMail an Apollo competitor?
No. Apollo is a prospecting and sequencing platform with a 270M-contact database. StackMail is mailbox infrastructure - we provision Google Workspace and Microsoft 365 mailboxes, configure DNS, and run warmup. Apollo connects to mailboxes; StackMail provides them. The two products live at different layers of the stack and a healthy cold email program usually has both. If you searched 'Apollo alternative' looking for something to replace Apollo with, StackMail is not it - you probably want a different sequencer (Instantly, Smartlead, Saleshandy, Lemlist) or a different lead database (ZoomInfo, Lusha, Cognism, Clay).
Can I use StackMail mailboxes with Apollo's sequencer?
Yes. Apollo accepts external Gmail and Outlook mailboxes via standard OAuth. StackMail-provisioned mailboxes are real Google Workspace or Microsoft 365 seats, so they connect to Apollo the same way any other Gmail or Outlook account does. The common pattern is: Apollo for the lead database and the sequencer, StackMail for the mailbox layer underneath. You drop StackMail mailboxes into Apollo's mailbox connections page via OAuth and Apollo sends through them. No middleware, no API gymnastics.
Why would I add StackMail underneath Apollo instead of just using my Gmail account?
Three reasons. First, deliverability isolation: cold email through your personal Gmail account or your company's primary Google Workspace tenant risks the reputation of the domain you actually need for legitimate email. StackMail provisions mailboxes on dedicated lookalike domains so cold email risk is fully isolated. Second, scale: Apollo's sequencer can saturate one or two mailboxes quickly. To run a real outbound program you need 10-50+ mailboxes across multiple domains, which means provisioning seats, configuring SPF/DKIM/DMARC for each, and running warmup. StackMail does that work. Third, sequencer flexibility: if you ever want to test Smartlead or Saleshandy alongside Apollo, your StackMail mailboxes connect to all three without re-warming.
Apollo has SOC 2 and ISO 27001. Does StackMail?
Apollo holds SOC 2 Type II, ISO 27001, GDPR, PCI, and CCPA certifications on its corporate envelope. StackMail is GDPR-compliant and our mailboxes operate inside Google Workspace's and Microsoft 365's compliance perimeters (which carry SOC 2, ISO 27001, HIPAA-eligible, and the rest), but our company entity does not yet hold an independent SOC 2 badge. For procurement-heavy enterprise customers who need our corporate badge, Apollo (or InboxKit, which has SOC 2) may be a better fit today. We are working on it.
Apollo's contact database is 270M. Does StackMail have a contact database?
No. We do not have a B2B contact database and we are not building one. The cold email category has dozens of dedicated prospecting tools - Apollo, ZoomInfo, Lusha, Cognism, Clay, RocketReach, LeadIQ, LinkedIn Sales Navigator - and competing with those on data depth would be a different company. StackMail is mailbox infrastructure. If you need contacts, pull them from Apollo or a comparable tool, then push them into your sequencer of choice, then send through StackMail mailboxes. Three layers, three specialists.
If I cancel Apollo, what do I lose?
You lose access to the contact database (your contact lists may export but ongoing enrichment stops), you lose any sequences that lived inside Apollo's sequencer, and you lose any deals tracked in Apollo's pipeline. The mailboxes connected to Apollo are not Apollo's - they are your Google Workspace or Microsoft 365 accounts (or your StackMail-provisioned ones), so those are unaffected by an Apollo cancellation. If you stay on Apollo and add StackMail mailboxes underneath, this question does not apply - you only lose what you choose to leave behind.
I want a real Apollo alternative for the lead database. Where should I look?
Depends on budget and territory. ZoomInfo is the premium option with the cleanest data and the highest enterprise price - expect $15,000-$50,000+ annual contracts. Lusha and Cognism are mid-market alternatives with strong EU coverage and per-seat pricing closer to Apollo's. Clay is the modern waterfall-enrichment option that pulls from multiple sources (Apollo, Lusha, ZoomInfo, LinkedIn) and is excellent for technical teams that want to script their prospecting. RocketReach and LeadIQ are lighter alternatives at lower price points. None of these are mailbox providers - you still need a mailbox layer underneath whichever lead source you pick.
I want a real Apollo alternative for the sequencer. Where should I look?
Instantly and Smartlead are the two specialized cold email sequencers that most agencies and growth teams use at scale. Saleshandy is a strong mid-market alternative with built-in warmup. Lemlist leans into multichannel (email plus LinkedIn) sequences. Outreach and Salesloft are enterprise sales engagement platforms that compete with Apollo's sequencer at the high end - expensive but deeper. Reply.io is a solid mid-market option. We have written deep comparison pages for several of these on the StackMail site - they are linked from /alternatives. The mailbox layer underneath any of these is StackMail.
Do StackMail and Apollo have any direct overlap at all?
Almost none. The only edge case is the email verifier - Apollo includes an email verifier as part of its product, and StackMail offers a free email verifier at stackmail.io/tools. If you cancel Apollo and want a free standalone verifier, ours works. That is the entirety of the overlap. Everything else Apollo does (contact database, sequencer, dialer, deal management, conversation intelligence) is outside our product scope, and everything StackMail does (mailbox provisioning, DNS automation, warmup, tenant isolation) is outside Apollo's product scope.
Should I use Apollo for cold email at all, or go straight to a specialized sequencer plus StackMail?
It depends on volume. If you are sending under 1,000 cold emails per week from one or two mailboxes and you also need a contact database, Apollo is the most economical bundle. If you are sending 5,000+ cold emails per week from 10+ mailboxes, the specialized stack (Apollo or another lead source for contacts, Instantly or Smartlead for sequencing, StackMail for mailboxes) is meaningfully more reliable and usually cheaper net. The crossover point in our experience is around 30 mailboxes - below that, the bundle is fine; above that, specialization pays off.
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