Cold email deliverability: domains, warm-up, daily volume

Cold email deliverability comes down to a few choices made before the first message goes out: which domain you send from, whether that domain proves who it is, whether the mailbox has built a sending history, and how much each mailbox sends per day. This guide goes through those choices in order. It ends with a checklist for before launch, daily and weekly.

For background on the term, see the glossary entries on deliverability and mailbox warm-up.

Who this is for

This guide is for you if:

You are about to send cold email for the first time and want the setup right before you start.
You already send, and replies or inbox placement have dropped, and you want a list to check against.
You run outbound for a small team and need to decide how many domains and mailboxes to set up.

It is not a guide to writing the email itself, and it does not tell you which markets to sell into.

Steps

1. Send from separate domains, not your main one

Keep cold email apart from the mail your team sends to customers. Buy one or more domains used only for outreach, and keep your main domain for everyday mail.

Outlevo's managed mailboxes are built around this idea. Outlevo buys the sending domains, creates the mailboxes through Zapmail, sets up DNS and warms them up, so you never touch your main domain. [[1]](#sources) You choose from the domains Outlevo proposes, and you give the sender names. Outlevo does the purchase, the DNS records, the mailboxes and the warm-up. [[1]](#sources)

The plan sets how many you get. Builder includes 1 domain and 2 mailboxes. Growth includes 2 domains and 4 mailboxes. [[1]](#sources) Sending, follow-ups and the mailboxes your plan includes use no credits. [[1]](#sources)

If you would rather use mailboxes you already own, connect your Smartlead account. Smartlead sends the emails from the mailboxes in that account, and Outlevo writes and schedules them. [[2]](#sources) Keep those mailboxes on separate sending domains, too.

Other tools take a similar approach. Artisan says it sends in reps' names from the customer's own sending domains, with warm-up managed (checked October 22, 2026). [[3]](#sources) 11x lists managed Gmail mailboxes as included, with domain setup and warm-up (checked October 22, 2026). [[4]](#sources) When you compare tools, ask two questions: whose domain is it, and who runs the warm-up?

2. Set up SPF, DKIM and DMARC

Set up SPF, DKIM and DMARC on every sending domain before any mailbox starts to warm up.

SPF has a limit on DNS-lookup terms. The standard says: "SPF implementations MUST limit the total number of those terms to 10 during SPF evaluation" (RFC 7208, checked October 22, 2026). [[5]](#sources) A long chain of includes can break SPF, so keep the record short on a domain that exists only for sending. [[5]](#sources)

DKIM adds a signature to each message. RFC 6376 describes it this way: "DomainKeys Identified Mail (DKIM) permits a person, role, or organization that owns the signing domain to claim some responsibility for a message by associating the domain with the message." (checked October 22, 2026) [[6]](#sources)

DMARC tells receivers what to do when a message fails those checks, and where to send reports. RFC 7489 says that "a mail-originating organization can express domain-level policies and preferences for message validation, disposition, and reporting" (checked October 22, 2026). [[7]](#sources) Yahoo's sender best practices say to "Publish a valid DMARC policy with at least p=none" (checked October 22, 2026). [[8]](#sources) Start at that level on a new domain and read the reports before you tighten anything.

Mailbox providers require these records at bulk volume. Below that volume, treat them as recommended, not required:

Gmail and Yahoo require SPF or DKIM for all senders, and SPF, DKIM and DMARC for bulk senders (checked October 22, 2026). [[9]](#sources)
Google says that "email senders who send more than 5,000 messages per day to Gmail accounts must meet the requirements in this section. Set up SPF and DKIM email authentication for your domain." (checked October 22, 2026) [[10]](#sources)
Microsoft says that "For domains sending over 5,000 emails per day, Outlook will soon require compliance with SPF, DKIM, DMARC." (checked October 22, 2026) [[11]](#sources)

Set up all three on every domain regardless of volume.

Outlevo enforces this when you connect Smartlead. Before a campaign sends, every mailbox must be connected and warmed up, and its domain must have SPF, DKIM and DMARC checked in the last 7 days. [[2]](#sources) An old pass does not count. If you change DNS, expect to re-check.

3. Warm up every new mailbox before it sends

A new mailbox has no history with the providers that receive its mail. Warm-up is the period in which it builds one. Do not skip it, and do not shorten it to hit a launch date.

With managed mailboxes, a new mailbox sends nothing until it is warm: at least 14 days, usually about 3 weeks. [[1]](#sources) Plan your launch around that. If you buy domains on Monday, do not promise a send date that week.

With your own Smartlead mailboxes, Outlevo reads each mailbox with its warm-up state from your Smartlead account. [[2]](#sources) A campaign will not send from a mailbox that is not warmed up. [[2]](#sources)

Warm-up does not end on the day sending begins. Outlevo checks each managed mailbox's warm-up state and reputation daily. [[1]](#sources) Treat that as the model for your own setup: look at mailbox state every day, not once at launch.

If you are asking how to warm up a new domain for cold email, the order is:

Buy the domain and create the mailboxes. With managed mailboxes, Outlevo does both. [[1]](#sources)
Publish SPF, DKIM and DMARC, and check them. For Smartlead campaigns, the check must be within the last 7 days. [[2]](#sources)
Start warm-up and leave the mailboxes out of campaigns. A managed mailbox sends nothing for at least 14 days. [[1]](#sources)
Connect only mailboxes that show as warmed up. [[2]](#sources)
Set a daily cap in the approved policy, since policies set how often you contact people. [[12]](#sources) Keep it low at first and raise it only while the signals stay clean.

4. Decide daily volume per mailbox

This is the question most people ask: how many cold emails per mailbox per day? No single number is right for every sender, and this guide does not give one. Your warm-up state, list quality and reply rate all move it. What you can do is set the limit deliberately and keep it visible.

Some framing helps:

The provider thresholds are totals. Google's 5,000 figure covers messages per day to Gmail accounts. [[10]](#sources) Microsoft's covers a domain's emails per day. [[11]](#sources) Neither is a target for one mailbox. A small setup should sit far below them, and the authentication steps above apply either way.
Volume is the sum of your mailboxes. More mailboxes means each one can send less for the same total. The Builder plan includes 2 mailboxes and Growth includes 4. [[1]](#sources) Work out the total you want, divide by the mailboxes you have, and set the cap below that share.
Set the cap in writing. In Outlevo, policies set who can be contacted, on which channels, how often and with what budget. Every external action is checked against the approved policy before it runs, and recorded in a ledger. [[12]](#sources) Nothing is sent outside a policy that a person approved. [[12]](#sources) Put the daily limit in that policy so a raised number is a decision someone made and not a drift.
Expect low reply rates. Belkins' 2026 study of 7.5M B2B emails sent in 2025 found that 0.45% of emails get a reply across industries (reply rate is replies divided by emails sent). [[13]](#sources) [[14]](#sources) You will not see replies fast enough to judge a mailbox on one day. Judge it on the trend.

Raise a mailbox's cap only after it has been stable at the current one. Change one thing at a time so you know which change caused a problem.

5. Verify addresses before you send

Check each address before it enters a campaign. Email verification costs 1 credit per check. [[15]](#sources) You can read more on the email verification page.

Outlevo reads sent, reply, bounce, unsubscribe and category-change events back from Smartlead by webhook. [[2]](#sources) Those events give you the bounce and unsubscribe counts to watch in the next section.

6. Keep a way to stop

Stopping quickly matters as much as setting up well. Kill switches in Outlevo pause a campaign, a channel or the whole workspace at once. [[12]](#sources) Decide ahead of time what makes you press one: a sudden run of bounces, a mailbox that drops out of warm-up, or a failed authentication check. Write those triggers down so nobody has to decide during an incident.

What to check

Run this list before launch and then on a schedule.

Before the first send

Each sending domain is separate from your main domain.
SPF, DKIM and DMARC are published, and the check is recent. For Smartlead campaigns it must be within the last 7 days. [[2]](#sources)
The SPF record stays within the 10-term lookup limit. [[5]](#sources)
Your DMARC policy is at least p=none. [[8]](#sources)
Every mailbox is connected and shows as warmed up. [[2]](#sources)
Addresses on the list have been verified. [[15]](#sources)
The daily cap per mailbox is written into the approved policy. [[12]](#sources)

Every day

Warm-up state and reputation for each mailbox. Managed mailboxes get this check daily. [[1]](#sources)
Bounces and unsubscribes arriving from Smartlead. [[2]](#sources)

Every week

Total volume across all mailboxes, against the provider thresholds that apply to you. [[10]](#sources) [[11]](#sources)
Whether authentication still passes after any DNS or tool changes.
Reply trend per mailbox, compared with where it started.

When a mailbox degrades, pause it and do not raise volume on the others to make up the difference. Look at the list, the authentication records and the warm-up state first.

This guide gives no bounce-rate or spam-complaint limits. Work out your own baseline from your first clean weeks, and treat a clear move away from it as the signal to pause.

Next step

Pick one route and start the clock on warm-up today, since it is the slowest part.

If you want Outlevo to run the domains: read how managed mailboxes work, and check the pricing page for what each plan includes.
If you already use Smartlead: read the Smartlead integration page, then confirm that your domains have recent SPF, DKIM and DMARC checks.
If you have not defined who to email yet: run the free ICP assessment. It reads up to 5 public pages of your website. [[16]](#sources) It returns facts labelled as verified observations or AI inferences, and up to 5 experimental segment hypotheses. [[16]](#sources)

A tidy setup does not fix a poor list. Get the targeting right, then set up the domains.