Before you compare SMTP prices, read the acceptable use policy. Amazon SES, SendGrid, Mailgun, and Postmark all restrict or prohibit unsolicited email, and their accounts get reviewed at roughly one spam complaint per thousand emails.
Before you compare SMTP prices, read the acceptable use policy. Amazon SES, SendGrid, Mailgun, and Postmark all restrict or prohibit unsolicited email, and their accounts get reviewed at roughly one spam complaint per thousand emails. Cold outreach crosses that line as a matter of course. SES at $0.10 per thousand emails is worthless if the account is suspended in week two.
What actually works for cold email over SMTP: your own Google Workspace or Microsoft 365 mailboxes, or purpose-built cold email infrastructure. This post covers what each major SMTP provider allows, the real pricing checked this month, and the setup that does not get you banned.
An SMTP provider for cold email is a service that relays outbound mail over the SMTP protocol. Transactional SMTP APIs such as Amazon SES, SendGrid, Mailgun, and Postmark are optimized for opt-in and system-generated mail and restrict cold outreach in their terms. Cold email over SMTP works through your own Google Workspace or Microsoft 365 mailboxes, or through infrastructure built specifically for cold sending.
For the big transactional APIs, mostly no. Their business is protecting shared IP pools, and they eject senders who generate complaints. Cold email to a real prospect list produces complaints above their thresholds, so the account gets flagged, throttled, and closed.
What is allowed:
| Provider | Cold email stance | Pricing | Dedicated IP add-on |
|---|---|---|---|
| Amazon SES | Prohibits unsolicited; suspends on complaints | $0.10 per 1,000 emails | Available, extra |
| SendGrid | Restricts cold; complaint reviews | From $19.95 / mo for 50k; ~$89.95 at 100k | $30 / mo per IP, up to 3 |
| Mailgun | Restricts unsolicited | Volume tiers | $59 / mo per IP |
| Postmark | Transactional only; rejects bulk and cold outright | Per-message credits | $50 / mo |
| Google Workspace SMTP | Allowed (your own mailboxes) | ~$6 to $12 / mailbox / month | N/A, shared |
| Cold email SMTP infra | Built for cold outreach | ~$2 to $4.50 / mailbox / month | Varies, rotation-based |
Three reasons, all structural. They run shared IP pools and one bad sender hurts everyone on the pool. Their complaint threshold is around 0.1%, which a cold list reaches easily. And they can detect the signature of cold sending: many recipients across unrelated domains, low prior engagement, list-shaped send patterns.
This is not a loophole to work around. It is the core of how these services stay deliverable for their intended customers. See dedicated IP vs shared IP email and why are my emails going to spam.
Connect real mailboxes to a sending platform over SMTP and IMAP. The two paths:
Both stay inside per-mailbox sending limits and rely on warm-up and list quality, not on a provider looking the other way.
Say you run 12 mailboxes sending 40 cold emails a day each, about 15,000 a month.
The transactional API looks 30 to 60 times cheaper on paper. It is not an option, because the pricing you are comparing is for mail you are not allowed to send.
If you send legitimate opt-in or transactional mail at scale and also want a dedicated IP, SendGrid at $30 per IP, Mailgun at $59, and Postmark at $50 are the reference points. But a dedicated IP only earns its keep above roughly 100,000 emails a month sent consistently. For cold email at 15,000 a month, it is the wrong layer to optimize, and the transactional providers do not want the cold traffic on the IP anyway.
Running your own mail server on a VPS is the maximum-control option and, for cold email, usually the wrong one. A fresh server IP has no reputation, sits in a hosting range that many filters distrust by default, and takes weeks of careful warm-up to become usable. You also inherit every operational job the managed providers handle: reverse DNS, TLS, feedback loops, blacklist monitoring, patching.
Teams that do this well are running real infrastructure engineering. Everyone else gets better deliverability, faster, from real Google Workspace or Microsoft 365 mailboxes on the platforms recipients actually use. See how to set up cold email infrastructure.
If a transactional provider has already flagged or closed your account for cold sending, do not open a new account with the same provider and resume. They log the domains and payment details, and a second strike escalates faster.
Move to the correct setup: buy secondary domains if the burned ones are also damaged, stand up Workspace or Microsoft 365 mailboxes, authenticate them, and warm them for 3 to 8 weeks before sending real volume. Check the old domains against a blacklist scan before deciding whether to keep them. Treat the suspension as the signal it is: the previous approach was structurally wrong, not unlucky.
The AUP-First Rule: before comparing SMTP providers on price, read the acceptable use policy. If it names "unsolicited," "purchased lists," or "cold outreach" as prohibited, the per-email rate does not matter, because the account will be suspended before it saves you anything.
The rule saves you from a common and expensive mistake: choosing an SMTP provider on the pricing page, wiring up a cold campaign, and losing the account plus the domain reputation two weeks later. The transactional APIs publish per-thousand rates that look irresistible next to Workspace's per-mailbox cost, and every one of those rates is priced for opt-in mail.
Run the check in order. First, does this provider's AUP permit cold outreach, explicitly or by virtue of it being my own mailbox? Only if yes do you compare price, deliverability, and rotation support. The quotable version: "The cheapest SMTP for cold email is the one that does not close your account."
Your own Google Workspace or Microsoft 365 mailboxes always pass the first check, because the AUP you are bound by is Gmail's or Microsoft's normal sending policy, not a transactional provider's bulk-mail restriction.
That does not make your mailboxes unlimited. Gmail and Microsoft still fold unsolicited mail on complaint and bounce rates, and still cap volume per account. The difference is that they will not close the account for the act of cold sending itself, the way SES or SendGrid will. You are inside a policy that tolerates outreach done responsibly, rather than one that prohibits it outright. Stay inside the per-mailbox sending limits, keep complaints low with a verified list, and the account stays healthy indefinitely.
Whatever SMTP path you choose, the thing that keeps the account alive is a low complaint rate, and that comes from sending relevant mail to real people.
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Transactional SMTP providers, Amazon SES, SendGrid, Mailgun, Postmark, are cheap because they carry opt-in and system mail, and their terms restrict or ban cold outreach. Their accounts get reviewed at about one complaint per thousand, which cold email routinely exceeds. For cold email over SMTP, use your own Google Workspace or Microsoft 365 mailboxes, or infrastructure built specifically for outreach, connected to a sequencer. Compare those on price only after confirming the use case is allowed, and put the saved effort into a verified list.
Can I send cold email through Amazon SES?
Not without risking suspension. SES prohibits unsolicited email in its acceptable use policy and reviews accounts that exceed roughly one complaint per thousand emails, which cold outreach reaches easily. The $0.10 per thousand pricing is for opt-in and transactional mail. Use your own mailboxes or cold email infrastructure instead.
What SMTP provider allows cold email?
Your own Google Workspace or Microsoft 365 mailboxes over SMTP, because you are bound by Gmail's or Microsoft's standard sending policy rather than a transactional provider's bulk restrictions. Beyond that, infrastructure built specifically for cold outreach accepts it as the intended use case and supports IP rotation.
Why do SMTP providers ban cold email?
They run shared IP pools and protect them by removing senders who generate complaints. Cold email produces complaint rates above their roughly 0.1% threshold, and they can detect its pattern: many recipients across unrelated domains with low prior engagement. Ejecting cold senders is how they stay deliverable for opt-in customers.
How much does cold email SMTP cost?
Google Workspace and Microsoft 365 mailboxes run $6 to $12 each per month. Dedicated cold email infrastructure runs roughly $2 to $4.50 per mailbox. A 12-mailbox setup sending 15,000 a month costs about $42 to $96 a month for mailboxes, plus a sending platform fee from around $47.
Do I need a dedicated IP for cold email SMTP?
No. A dedicated IP only pays off above roughly 100,000 emails a month sent consistently. A typical cold operation sends around 15,000 a month, far below that, and transactional providers that sell dedicated IPs do not want cold traffic on them regardless. Stay on shared infrastructure.
Is SendGrid or Postmark better for cold email?
Neither. SendGrid restricts cold outreach and reviews accounts on complaints; Postmark is transactional-only and rejects bulk and cold mail outright. Both are good at what they are built for, which is not cold email. Use real mailboxes on a sequencer.
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