Cold email deliverability and inbox warmup tools
Deliverability depends on authenticated domains (SPF, DKIM, DMARC), mailbox reputation, sending volume and content people want. Tools here cover parts of that: buying sending mailboxes, warming them, testing inbox placement and monitoring DMARC. None of them fixes unwanted email.
Prices verified on vendor pages for 9 of 10 providers below; the rest are marked unknown. Always confirm at checkout. Order: vendor discounts, then free tiers, then standard signups, A–Z. Affiliate status does not affect order.
Comparison table
| Provider | Offer | Published pricing (verified) | Free option |
|---|---|---|---|
| DMARCLY | Standard signup | Pricing per dmarcly.com/pricing (monthly/annual toggle; confirm at checkout): Professional $17.99/mo, Growth $39.99/mo, Business $69/mo, Enterprise $199/mo; overage $10 per 1M emails over quota, $1 per extra DMARC domain, $10 per extra Safe SPF domain. 14-day free trial, no credit card required. | Yes |
| Folderly | Standard signup | Pricing per folderly.com/pricing: sender reputation maintenance $96 per mailbox/month billed yearly (save 20%); inbox placement tests free 2/mo, $79/mo for 100 tests/month, or $799/yr (save 15%); spam-placement alerts $0/mo. A 10% referral coupon was not shown on folderly.com; verify at checkout. | Yes |
| Heyo Email | Standard signup | Cold-email sending: unlimited sending accounts (Microsoft Exchange OAuth), automatic peer-to-peer warmup, global unibox, multi-step sequences with A/B tests, DNC management, REST API; Heyo Infra Exchange mailboxes ~$0.34-0.44/mo. Starter $39/mo (50k emails), Growth $79/mo (200k emails), Agency whitelabel $49/mo (per … | Not verified |
| InboxKit | Standard signup | Flat $3.00/mailbox/mo monthly or $2.50 annual (quarterly 10% off), no plans or minimums; Azure $30/tenant/mo (up to 100 mailboxes); warmup add-on $3/mailbox/mo; pre-warmed mailboxes $6–$9/mailbox/mo plus domain fee from $12.50; free account, no card; no promo code (per inboxkit.com/pricing). | Not verified |
| MailReach | Standard signup | Pricing calculator shows email warmup at $19.5 per mailbox per month (total varies by mailbox count, volume discounts shown) and spam-test credits sold in packs; custom quote for 100+ mailboxes / 10,000+ credits (per mailreach.co/pricing). | Not verified |
| Premium Inboxes | Standard signup | unknown | Not verified |
| ReachInbox | Standard signup | Free plan (3 accounts, 250 emails/mo); Starter $30/mo, Growth $75/mo, Pro $225/mo billed yearly; Enterprise $999/mo (per reachinbox.ai/pricing). | Yes |
| Relay (userelay.app) | Standard signup | Per userelay.app: plans from $10/mo, mailboxes as cheap as $1/mo at volume, SPF/DKIM/DMARC compliant, credentials CSV within 24h for Instantly/Lemlist import. | Not verified |
| Salesforge (Forge suite) | Standard signup | Salesforge: cold outreach with unlimited mailboxes, warm-up, mailbox rotation, AI personalization, LinkedIn steps, API, and AI SDR Agent Frank; 14-day free trial; pricing page lists plans from $40/mo and states 'starting at $48/mo' (per salesforge.ai/pricing). | Yes |
| Zapmail | Standard signup | Growth 30, larger tier 100) with additional mailboxes at $3.00-$3.50 each and deliverability test credits (per zapmail.ai). | Not verified |
Pros and cons
Derived only from facts on the vendor pages we checked.
DMARCLY
Pros:
- Free plan, trial or credits to test before paying
- No card required to start (per vendor page)
- Pricing is published, so you can budget before signing up
Cons:
- Some plans or trials require a card
- Some terms could not be confirmed on the public page; verify at checkout
Folderly
Pros:
- Free plan, trial or credits to test before paying
- Pricing is published, so you can budget before signing up
Cons:
- Some terms could not be confirmed on the public page; verify at checkout
Heyo Email
Pros:
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
InboxKit
Pros:
- No card required to start (per vendor page)
- Offers an MCP server or agent integration
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
MailReach
Pros:
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
Premium Inboxes
Pros:
- None verified beyond the listing
Cons:
- No verified public price in our records; you must check the vendor site
ReachInbox
Pros:
- Free plan, trial or credits to test before paying
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
Relay (userelay.app)
Pros:
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
Salesforge (Forge suite)
Pros:
- Free plan, trial or credits to test before paying
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
Zapmail
Pros:
- Pricing is published, so you can budget before signing up
Cons:
- Limits and overage rates vary by plan; read them before committing
How to choose
- Fix authentication first: SPF, DKIM and a DMARC policy. A DMARC monitor shows what is failing.
- Price mailboxes per mailbox per month, including domain costs and any warmup add-on.
- Use placement tests to measure, not guess, before scaling volume.
- Keep volume per mailbox modest and honor opt-outs; warmup cannot rescue a list that complains.
- Comply with CAN-SPAM, GDPR and other anti-spam laws.
FAQ
Does inbox warmup work?
Warmup can help a new mailbox build sending history, but reputation ultimately follows recipient engagement and complaint rates.
How much do cold email mailboxes cost?
Verified per-mailbox prices are in the table; compare including domain and warmup add-ons.
Do I need DMARC?
Major mailbox providers expect SPF, DKIM and DMARC for bulk senders; monitoring helps you reach an enforced policy safely.
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Categories: Email API deals
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