Cold email infrastructure, reviewed
The independent index of
cold email mailbox providers
Compare mailboxes for cold outreach — Google Workspace, Microsoft 365 and dedicated SMTP — on price, IP model and reviews. Built for senders using Instantly, Smartlead, Saleshandy, Reachinbox and other sequencers.
Show prices for
25 providers
Aerosend Pre-warmed
Private SMTP cold-email infrastructure provider offering dedicated per-batch IP isolation, managed warmup, and domain health monitoring — targeted at agencies running 30+ mailboxes with their own domains.
from $4.00/mb
$4.00
↓ $2.00 at scale
Dedicated IPs · US 24–48 hrs 30+ mailboxes
4.6★ (5)
G2 4.6
Volume-priced Google Workspace reseller targeting cold-email agencies with same-day delivery and a developer API, though independent reviews question whether accounts are truly pre-warmed and note limited company transparency given the domain was registered in August 2024.
from $3.50/mb
$3.50
↓ $2.80 at scale
Unknown · US same day API 1+ mailboxes
4.7★ (26)
Trustpilot 4.7
ColdSire sells Google Workspace and Microsoft 365 mailboxes at a flat $6/mo per account, claiming deliverability advantage from housing cold-email accounts in a mixed-use infrastructure pool alongside real businesses.
from $6.00/mb
$6.00 $6.00
Unknown · US ~5 minutes
2.6★ (6)
Trustpilot 2.6
Email Astra Pre-warmed
Pre-warmed GWS and M365 accounts aimed at cold-email agencies that want to skip the warmup window, sold with dedicated US IPs and DNS pre-configuration at month-to-month rates from $4–$7/mailbox depending on platform.
from $7.00/mb
$7.00 $7.00
Dedicated IPs · US immediate 6+ mailboxes
3.7★ (1)
Trustpilot 3.7
Automated Azure-native cold email infrastructure service that provisions dedicated-tenant mailboxes (Azure/Entra, GWS, M365) in 4–6 hours, sold in flat-rate monthly orders with a built-in warmup process required before sending.
from $0.50/mb
$0.50 $0.50 $0.50
Dedicated tenant · US 4–6 hrs 50+ mailboxes
3.2★ (1)
Trustpilot 3.2
A US-IP mailbox provisioning service offering Google Workspace, Microsoft 365, and Azure accounts with automated DNS setup, sold in bundle tiers starting at 10 mailboxes, with warmup and monitoring available as paid add-ons.
from $3.90/mb
$3.90 $3.90 $3.90
Shared IPs · US 30–120 minutes API 10+ mailboxes
4.9★ (34)
G2 4.9
Private SMTP infrastructure with dedicated IPs and automated DNS setup, targeting cold-email agencies that want to avoid shared IP pools; pre-warming is marketed as included but the underlying servers are not GWS or M365.
from $4.00/mb
$4.00
↓ $3.00 at scale
Dedicated IPs · US/EU 5 minutes API 10+ mailboxes
4.7★ (58)
G2 4.8 TP 3.7
Flat-rate SMTP infrastructure on Microsoft-backed dedicated IPs offering unlimited mailboxes per monthly plan — cost-effective for high-inbox-count agencies but requires external warmup tools and is limited to Microsoft servers with no Google Workspace option.
Capacity-based
Dedicated IPs · US ~3 min API 40/day
4.6★ (33)
Trustpilot 4.6
Fresh and pre-warmed GWS + M365 mailboxes on dedicated IPs with automated DNS setup; pre-warming is a separate higher-priced tier
from $3.70/mb
$3.70 $3.70
↓ $2.83 at scale
Dedicated IPs · US/EU 12 hrs API 10+ mailboxes 25/day
4.5★ (16)
Trustpilot 4.5
Multi-platform cold email infrastructure provider offering Microsoft 365 tenants, Google Workspace, and private SMTP under one roof, with volume-tiered pricing and a pre-warmed Outlook add-on tier.
from $3.45/mb
$3.45 $3.45 $3.45
↓ $2.99 at scale
Dedicated IPs · US/EU Instant API 10+ mailboxes
4.3★ (9)
Trustpilot 4.3
Budget-focused cold-email mailbox provider offering proprietary SMTP and Google Workspace accounts at competitive per-mailbox rates, with automated provisioning and IP rotation, but no included pre-warming and shared IP infrastructure.
from $2.50/mb
$2.50 $2.50
↓ $0.50 at scale
Shared IPs · US/EU 5 min API 30+ mailboxes 15/day
4.6★ (199)
G2 4.6 TP 3.7
Self-service shared-SMTP cold email infrastructure with sub-$3/mailbox pricing and automated DNS setup, targeting volume senders who accept shared-IP deliverability trade-offs and handle warming separately.
from $3.00/mb
$3.00
Shared IPs · US under 10 min 10+ mailboxes 30/day
4.5★ (98)
G2 4.7 TP 3.5
Multi-platform cold-email infrastructure (Google Workspace, Microsoft 365, and SMTP) on dedicated IPs with automated DNS and API access, aimed at agencies running 200-1,000+ inboxes; warmup is not included so a separate tool is required.
from $1.50/mb
$1.50 $1.50 $1.50
↓ $1.50 at scale
Dedicated IPs · US 1 day API 200+ mailboxes
—
Self-serve cold email infrastructure offering SMTP, Google Workspace, and Microsoft 365 mailboxes with automated DNS setup starting at $3/inbox/mo; warming is not included and users must handle it separately.
from $3.00/mb
$4.00 $5.00 $3.00
Shared IPs · US/EU ~5 min API 1+ mailboxes
4★ (4)
Trustpilot 4
Dedicated private mail server provider at a flat monthly rate (~$249/month for up to 200 mailboxes), using custom SMTP infrastructure on OVH/UpCloud rather than Google or Microsoft, aimed at high-volume cold email agencies wanting full IP isolation.
Capacity-based
Dedicated IPs · US 24–48 hrs API 50/day
—
Proprietary SMTP infrastructure provider offering tiered capacity plans for bulk cold-email mailbox creation, with automated DNS setup, built-in warmup tooling, and a deliverability guarantee on its own domains.
No public pricing
Shared IPs · US ~1 hour
4.4★ (150)
G2 4.8 TP 4.2
SMTP infrastructure platform with dedicated IPs and pre-send content scanning, sold as a monthly subscription starting at $199 for 30 mailboxes; API access requires the $599/month Pro tier.
from $6.63/mb
$6.63
↓ $1.50 at scale
Dedicated IPs · US ~5 minutes API 30+ mailboxes
4.3★ (9)
Trustpilot 4.3
Managed inbox provider offering Google Workspace and Microsoft Azure mailboxes with built-in burn detection, real-time deliverability monitoring, and automatic inbox replacement.
from $3.50/mb
$3.50 $3.50
↓ $2.80 at scale
Unknown · US 2-48 hours API 1+ mailboxes
—
Premium Inboxes Pre-warmed
A done-for-you GWS and M365 mailbox provisioning service that handles DNS setup and warmup initiation, with tiered volume pricing, US infrastructure, unlimited replacements, and no API access.
from $3.50/mb
$3.50 $3.50
↓ $2.80 at scale
Unknown · US under 6 hours 1+ mailboxes
4.9★ (409)
Trustpilot 4.9
Slot-based provisioner of real Google Workspace and M365 mailboxes with automated DNS setup and US IPs; warming and monitoring sold separately through sibling products Warmforge and Infraforge.
from $4.50/mb
$4.50 $4.50
Shared IPs · US ~30 minutes API 10+ mailboxes
3.9★ (8)
Trustpilot 3.9
Infrastructure-focused reseller offering managed Google Workspace and Microsoft 365 mailboxes for cold email, with DNS pre-configured and an optional pre-warmed tier at a price premium.
from $0.35/mb
$3.00 $0.35
Shared IPs · US 24–72 hrs 10+ mailboxes
4.5★ (37)
Trustpilot 4.5
Managed infrastructure for agencies; conservative sending limits, proactive deliverability support
from $2.00/mb
$3.50 $2.00 $3.50
Dedicated tenant · US 2–4 days 25/day
4.6★ (17)
Trustpilot 4.6
Privately operated SMTP infrastructure for high-volume cold email, emphasizing the lowest per-mailbox cost, a full REST API (plus an MCP server), optional dedicated IPs, and a 90%-deliverability-or-refund guarantee on month-to-month billing.
from $1.38/mb
$1.38
↓ $0.95 at scale
Shared IPs · US under 10 minutes API 50+ mailboxes
4.6★ (19)
Trustpilot 4.6
Managed private-SMTP provider giving each client a dedicated server and IP, with automated deliverability monitoring and warmup scheduling — though users still supply their own warmup tool.
Capacity-based
Dedicated IPs under 48 hours 8+ mailboxes 75/day
—
Automated provisioner of Google Workspace and Microsoft 365 cold-email mailboxes with fast DNS setup, shared US/EU IPs, and optional pre-warmed accounts as a separate product tier.
from $3.90/mb
$3.90 $3.90
↓ $3.00 at scale
Shared IPs · US/EU 5-10 minutes API 10+ mailboxes 15/day
4.5★ (84)
G2 3.9 TP 4.5
No providers match these filters.
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Real reviews, not marketing
We aggregate verified ratings from G2, Trustpilot and (soon) real cold-email operators — so you compare on consensus, not testimonials.
Normalized pricing
Plans are reduced to a comparable price-per-mailbox so a $39/10-inbox plan and a $199/30 plan sit on the same axis.