MastroSDR.

Guide

Set up cold email without
burning your company domain

Four routes, cheapest first. What each one costs, how much it can actually send, and the three cheap options that cost more than they save. The first route is free and we mean it.

Start for $0

50 a day per mailbox, enforced in code.

Everything below follows from one decision

Sending reputation attaches to a domain. Not to a mailbox, not to a campaign, and not to the tool. That single fact decides the whole shape of the setup.

It means a domain that gets marked as spam stays marked, and fixing the DNS afterwards does not bring it back. It means the domain your invoices and client replies go out on is the one thing you cannot afford to spend. And it means buying a second domain is not a growth tactic, it is a blast radius decision.

The rule the rest of this page is built on

Cheap domains, expensive mailboxes, full authentication, slow warming, small caps, clean lists, and monitoring that tells you a domain is dying before the reply rate does.

The four routes

Ordered by what they cost. The right one is the cheapest that carries the volume you actually need, and most people need less than they think.

RouteDomainsMailboxesMailboxes a monthSends a day
The mailbox you already haveNone1Nothing50
One outreach domain12$14100
Two domains, four mailboxes24$28200
Four domains, eight mailboxes48$56400

The mailbox column prices a $7 seat at Google Workspace or Microsoft 365, which is what this page recommends and why. Cheaper seats exist, and the questions below say what they cost you. Domains are about $11 a year each on top, at a registrar selling at cost.

Prices checked August 2026, and every provider on this page changes them without telling anybody, so confirm before you buy.

  1. Route 1

    The mailbox you already have

    Free, and right until you need more than 50 sends a day.

    Mailboxes a month
    Nothing
    Domain fees a year
    None
    Sends a day
    50

    Right for you if. Finding out whether anyone replies to you at all, before spending a penny on infrastructure.

    • Connect the Gmail, Outlook or SMTP mailbox you already use.
    • Send at 10 a day and read what comes back.
    • Move up when you want more than 50 a day, which one mailbox cannot carry, or when outreach stops being something you do between jobs.

    What it costs you

    You are spending your real domain's reputation. Unlikely at 10 a day with every first email reviewed, and unrecoverable if it happens: your invoices and client replies go to spam with it, and fixing the DNS afterwards does not bring it back. A domain bought for the job costs $11 a year.

  2. Route 2

    One outreach domain

    Two mailboxes at about $14 a month, plus $11 a year for the domain. The first setup that puts your real domain out of reach.

    Mailboxes a month
    $14
    Domain fees a year
    $11
    Sends a day
    100

    Right for you if. One person selling one thing, who now knows the replies are there.

    • Buy a lookalike domain at cost from a registrar that does not mark up renewals. try-yourname.com, getyourname.com, yourname.co.
    • Put a real page on it. One page is enough. A domain with mail records and no website is the easiest thing in this list for a filter to spot.
    • Add two mailboxes on it from Google Workspace or Microsoft 365, at about $7 a seat. A dedicated cheap provider works if $14 is what stops you starting, and costs you the pool you were paying to borrow.
    • Publish SPF, DKIM, DMARC and MX, then let it sit for two weeks before the first send.

    What it costs you

    One domain is one point of failure. If it burns you are back to buying and warming another, and that is 21 days before you can send properly again.

  3. Route 3

    Two domains, four mailboxes

    Four mailboxes at about $28 a month, plus $22 a year for the domains. Losing one domain stops half your sending, not all of it.

    Mailboxes a month
    $28
    Domain fees a year
    $22
    Sends a day
    200

    Right for you if. A small team, or one person whose outreach is now the thing that fills the calendar.

    • Two domains, two mailboxes on each.
    • Split them across Google and Microsoft. Same argument as two domains: one suspended account or one degraded pool takes half your sending rather than all of it.
    • Warm both domains at the same time, so the second is ready before you need it.
    • Keep a record: which domain, bought when, first send, retired when.

    What it costs you

    Twice the DNS to get right, and every record has to be correct on both. A domain that is three quarters configured sends mail that fails authentication, and there is no partial credit from a receiver.

  4. Route 4

    Four domains, eight mailboxes

    Eight mailboxes at about $56 a month, plus $44 a year for the domains. Enough volume that a burned domain is an inconvenience.

    Mailboxes a month
    $56
    Domain fees a year
    $44
    Sends a day
    400

    Right for you if. A team where outbound is somebody's actual job, and pausing it costs real money.

    • Four domains, two mailboxes each, bought a few weeks apart rather than all at once.
    • Retire and replace on a schedule instead of in an emergency. Domains are consumable.
    • Watch each domain separately in Google Postmaster Tools. Reputation is a property of the domain, not of the campaign.

    What it costs you

    This is the point where somebody has to own it. Eight mailboxes, four record sets and four reputations is a job, and the failure mode is nobody noticing a domain going quiet for a fortnight.

Save on the domains. Never save on the mailboxes. That one is not a saving, it is a bill that arrives as silence.

Three cheap options that cost more than they save

These are not the bottom rung of the same ladder. They are a different decision that looks like the bottom rung.

Mail included with shared hosting

Free with the plan you already pay for

The sending address is shared with every other site on that server. One campaign that generates complaints gets the address blocklisted, and it takes down mail for everyone on it, including any client sites you host. Most shared hosting terms also prohibit bulk and unsolicited mail outright, and the penalty is suspension rather than a warning.

Running your own mail server on a VPS

About $5 a month

A new server has no sending reputation at all, and several hosting providers have ranges that large filters treat with suspicion before you send anything. You would be spending months earning what a $7 mailbox borrows on day one. It is a fine machine for the wrong job.

A transactional email provider

Often free below a few thousand sends

Read the acceptable use policy before assuming it will work. These services are built for mail the recipient asked for, and several prohibit cold outreach in terms. MastroSDR removed its own sending route through one of them for exactly that reason: the code worked, the policy did not allow it, so the route was deleted rather than left in place to get somebody's account closed.

What every route needs, whichever you pick

None of this costs money. All of it costs attention, and skipping any one of them makes the rest of the spend pointless.

SPF, DKIM and DMARC, on every sending domain
Gmail and Yahoo have required all three of bulk senders since 2024, and cold outreach is judged by the same machinery. One SPF record only, because two is a hard failure. Start DMARC at p=none with a reporting address, read the reports for a fortnight, then tighten.
MX records, even on a domain that only sends
Bounce notifications arrive as mail. Without an MX record you cannot receive the messages telling you an address is dead. A domain with no MX also looks disposable to the systems deciding whether to trust it.
Three weeks of warming, per domain
Reputation belongs to the domain, so a new mailbox on a warm domain inherits most of it and a new domain starts from nothing however many mailboxes sit on it. MastroSDR ramps every new mailbox from 10 a day over 21 days and will not let you skip it.
A hard cap of 50 a day per mailbox
Thirty to fifty an inbox a day circulates everywhere and nobody sources it, so this page does not repeat it as guidance. Two numbers here are genuinely published: Google, Yahoo and Microsoft each state a 0.3% spam complaint ceiling, and Google treats you as a bulk sender past five thousand a day (support.google.com/mail/answer/14229414). That 50 in the heading is our own choice rather than a citation, and MastroSDR enforces it in code rather than in a settings field, so no number anyone types raises it. More throughput comes from another mailbox on another domain, and there is no monthly cap above that on a paid plan.
A verified list, and a bounce rate under two percent
Over five percent and providers start throttling the address. MastroSDR checks every address can receive mail before spending a send on it, and a hard bounce goes on a do-not-contact list permanently rather than being retried.
One-click unsubscribe and a postal address, in every message
The List-Unsubscribe and List-Unsubscribe-Post headers of RFC 8058, which Gmail and Yahoo require, plus the physical address CAN-SPAM requires. An unsubscribe has to apply to mail already sitting in the queue, which is the most common way a system that is compliant on paper still generates complaints.
Open tracking switched off
A tracking pixel costs you deliverability and buys data that no longer means anything. Apple Mail Privacy Protection loads the pixel for around half of all recipients whether or not a person opened it. Any logic built on open rate is built on noise.
Somewhere to see the spam rate
Google Postmaster Tools is the only place a complaint rate exists: somebody pressing Report spam tells Google and tells you nothing. Verify each sending domain there. Keep the rate under 0.1%, because Google acts at 0.3% and problems start well below it.

Questions people ask before buying anything

You can, and it is the wrong domain to spend. Reputation attaches to the domain, so a campaign that goes badly follows your invoices, quotes and client replies into spam, and correcting the DNS afterwards does not undo it. Send from the mailbox you already have while you are finding out whether anybody answers. Move to a domain bought for the job before you need more than 50 a day.

Divide the number of emails you want to send in a day by 50, and round up. That is the honest arithmetic, because 50 a day is the most any one address should carry in cold outreach. A hundred a day is two mailboxes. Four hundred a day is eight, on four domains.

Between four and six weeks in total. Two weeks of the domain simply existing before the first send, because a domain registered days before a campaign is a well known spam signal, then 21 days of ramping volume. MastroSDR handles the second half automatically and starts every new mailbox at 10 a day.

No, and it is the one line in the budget worth protecting. Three tiers, not two. Mail bundled with shared web hosting is never the answer: one campaign's complaints take down every site on that server. A dedicated provider like Zoho or Titan does work, on a pool shared with strangers whose sending you cannot see. Google Workspace and Microsoft 365 cost $7 because you are renting their standing with the receiving side from day one.

Read the acceptable use policy first, because several of them prohibit it in terms. MastroSDR removed its own sending route through one of these providers for exactly that reason. The code worked; the policy did not allow it. Cold outreach belongs in a mailbox you own, which is also where the replies need to land.

Only if you are rewriting links, and the better answer is not to. A shared tracking domain inherits the behavior of every other sender using it, so a blocklisting somebody else earned lands on you. MastroSDR does not rewrite links or embed a pixel at all, so there is no tracking domain to buy.

Yes. Bounce notifications arrive as mail, so a send-only domain with no MX record cannot receive the messages that tell it an address is dead. A domain with no MX also reads as disposable to the systems deciding whether to trust it.

Three signals, in the order they arrive. Google Postmaster Tools reports a spam rate per domain, and anything at 0.3% is already serious. Your bounce rate crossing two percent means the list wants cleaning. A reply rate that halves against its own recent baseline usually means filtering rather than worse copy, and MastroSDR pauses a campaign when it sees that, because nothing else in a send log ever will.

The kind that trades mail between seeded accounts is worth nothing and carries real risk. Google gave GMass the choice between shutting its warmup network down and losing Gmail API access in January 2023, and Apollo dropped its own the year after. What actually warms a domain is real mail to real people at a volume that climbs slowly, which needs no product beyond a limit that refuses to move.

Between nothing and about $56 a month, and the difference is entirely how many mailboxes you need. Domains are roughly $11 a year each at a registrar selling at cost. Mailboxes are $6 to $7 each per month. Everything else on this page, the DNS records, the warming, the monitoring, is free and costs only attention. Prices checked August 2026.

MastroSDR enforces the whole list

It publishes and verifies every record on a new domain, ramps each mailbox from ten a day, refuses to send above 50, writes during the recipient’s working day rather than yours, and stops a mailbox before a provider does. Start on route one with the mailbox you already have.

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