Overview — What Each Platform Does
ColdRelay
ColdRelay provisions Microsoft 365 mailboxes on dedicated, isolated Azure tenants with dedicated IPs. Per-mailbox pricing: $1 (1-199), $0.85 (200-999), $0.70 (1K-4,999), $0.55 (5K+). Includes 100-150 mailboxes per domain, auto DNS, no warmup wait, 95% inbox guarantee, 60-minute setup, and a minimum of 50 mailboxes.
Mailforge
Mailforge is a cold email infrastructure platform offering automated mailbox and domain provisioning. Mailbox slot pricing is $3/slot/month on monthly billing, dropping to $2/slot on annual billing, with volume discounts down to ~$1.67/slot at bulk. A minimum of 10 mailbox slots is required (~$30/month floor). Mailforge is infrastructure only — there are no separate campaign-management plans; you pay for the slots and domains you provision via a usage-based calculator. The platform emphasizes automated setup, shared IP infrastructure, and universal SMTP integration. Domains purchased through Mailforge cost $14/year, with optional SSL/domain-masking add-ons.
Feature Comparison
| Feature | ColdRelay | Mailforge |
|---|---|---|
| Price per Mailbox (Base) | ✓ $1/mailbox (1-199 volume) | ~$3/mailbox starting price |
| Price per Mailbox (Volume) | ✓ $0.55/mailbox at 5K+ | $1.67-$1.75/mailbox at bulk volume |
| Infrastructure Type | ✓ Dedicated IPs on isolated Azure tenants — per-customer isolation | Shared IP infrastructure — purpose-built for cold email but shared across users |
| Mailbox Technology | ✓ Microsoft 365 (Exchange/Azure) — recognized and trusted by receiving servers | Custom SMTP infrastructure — purpose-built, but may receive different treatment from receiving servers |
| DNS Configuration | Fully automated SPF, DKIM, DMARC | Automated DNS configuration (DKIM, DMARC, SPF) included |
| Campaign Features | Infrastructure only — pairs with sending platforms | Infrastructure only — no built-in campaign management |
| Minimum Order | 50 mailboxes ($50/month) | ✓ 10 mailbox slots (~$30/month) |
| Free Plan | No free plan | No free plan — billed per mailbox slot (10-slot minimum) |
| Warmup | ✓ No warmup required — send from day 1 | Warmup approach not detailed — infrastructure focus |
| Inbox Guarantee | ✓ 95% inbox placement guarantee with money-back promise | No published inbox guarantee |
| Annual Discount | Volume-based discounts only | ✓ Annual billing drops slots to ~$2 vs $3 monthly (~33% off) |
| Slot Flexibility | ✓ Active mailboxes — pay for what you use | Slot-based — pay for slots whether or not all have active mailboxes, but can delete/recreate within slots |
Where ColdRelay Wins
ColdRelay's dedicated IP and isolated tenant infrastructure is a fundamental quality advantage over Mailforge's shared IP model. When you share IPs with other cold email senders, your deliverability is affected by their sending practices — one bad actor can damage your reputation. ColdRelay's isolated tenants eliminate this risk entirely. Pricing is also significantly better: $1/mailbox on ColdRelay vs. ~$3 on Mailforge at base volume. At scale, ColdRelay's $0.55 beats Mailforge's $1.67-$1.75. The 95% inbox guarantee with money-back promise provides concrete assurance that Mailforge doesn't match. Microsoft 365 mailboxes also carry inherent reputation advantages over custom SMTP infrastructure.
Where Mailforge Wins
Mailforge offers a lower entry point with 10 mailbox slots minimum (~$30/month) — making it accessible for very early-stage operations. Annual billing drops the per-slot rate to ~$2 (from $3 on monthly), which helps reduce long-term costs. The slot-based model lets you delete and recreate mailboxes without additional cost, which is useful for operations that frequently rotate infrastructure. Mailforge is a convenient, low-friction option for smaller operations.
✓ Choose ColdRelay If…
Choose ColdRelay if infrastructure quality, deliverability, and IP isolation are priorities. ColdRelay is the better choice for any operation where shared IPs are a concern — which is most serious cold email operations. The per-mailbox pricing advantage and inbox guarantee make ColdRelay the stronger value at every volume tier above 50 mailboxes.
Choose Mailforge If…
Choose Mailforge if you're testing cold email at very small scale (under 50 mailboxes) and want a low entry point. The 10-slot minimum (~$30/month) makes Mailforge an accessible starting point for experimentation. If you frequently rotate mailboxes and value the slot-based model, Mailforge's approach can be convenient.
The Verdict
ColdRelay delivers superior infrastructure at a lower price point. Dedicated IPs and isolated tenants are a clear quality advantage over Mailforge's shared IP model — especially at scale where shared infrastructure risks multiply. ColdRelay is cheaper at every volume level and offers a concrete inbox guarantee. Mailforge has a lower entry barrier, making it suitable for early-stage testing, but operations serious about deliverability will outgrow shared infrastructure quickly.
Frequently Asked Questions
Why does infrastructure isolation matter?
Shared IPs mean your sending reputation is affected by all other senders on the same IP. If someone else sends spam, your deliverability suffers. ColdRelay's dedicated IPs on isolated tenants mean your reputation is entirely your own. Mailforge uses shared IP infrastructure.
Does Mailforge have a free plan?
No. Mailforge is infrastructure billed per mailbox slot, with a 10-slot minimum (~$30/month) — there's no free tier. ColdRelay also has no free plan, but backs its infrastructure with a 95% inbox guarantee and money-back promise at $1/mailbox.
How does Microsoft 365 compare to Mailforge's SMTP infrastructure?
Microsoft 365 mailboxes benefit from Microsoft's trusted sender reputation. Custom SMTP infrastructure (like Mailforge's) can work well but may receive different treatment from receiving servers that prioritize known email platforms.
Which scales better?
ColdRelay. Volume pricing drops to $0.55/mailbox at 5K+ with guaranteed isolation maintained at every level. Mailforge's shared infrastructure means scalability comes with proportionally more shared IP risk.
Can I use both for different campaigns?
Some operations use different infrastructure providers for different campaign types. You could use ColdRelay for your primary high-value campaigns (where deliverability matters most) and Mailforge for testing or lower-stakes outreach.