Mailbox warm-up and deliverability
Use Vetta's outbound infrastructure of managed domains, mailboxes, and the warm-up network to build sender reputation before scaling cold email.
Updated October 25, 2026 · 7 min read
Cold email lives or dies on deliverability. A brand-new mailbox that suddenly sends dozens of emails a day lands in spam, and can burn the domain it sends from. Vetta's Email Infrastructure gives you the infrastructure to do this properly: dedicated sending domains, managed mailboxes, and a warm-up network that builds sender reputation before you go live.
You'll find it under Settings > Workspace > Email Infrastructure (the page is titled Email Deliverability Infrastructure). The header has Create domains, Manage mailboxes and Warm-up, and a summary shows your Active domains, SSL domains, Mailbox slots, Active mailboxes and IP addresses, each with a + to add more.
Why separate sending infrastructure
Never run cold outbound from your main company domain. If those sends get flagged, it affects every email your company sends, including invoices and support. The standard play, which Vetta manages end to end:
- Buy lookalike domains (yourcompany-hq.com, tryyourcompany.com)
- Create a few mailboxes per domain
- Warm them up for weeks
- Send within daily limits, spread across mailboxes
Domains
Click Create domains to open the domain wizard. Start by picking the mailbox product the domains are for. From there you can:
- Check availability and purchase sending domains (priced per year, with auto-renew)
- Use the Domain auto generator: enter your Primary domain and the Number of domains, then click Generate domains. Vetta suggests lookalike names and checks each one ("Available" with its yearly price); you can edit or delete any of them, and the Next button shows the running total
Settings · Email Infrastructure- Configure domain forwarding in the DMARC & Forwarding step (Forward to URL is recommended) so anyone visiting your sending domains is redirected to your real website: a legitimacy signal for both prospects and filters
- Set a DMARC email to receive DMARC reports (use sparingly: the volume is high)
- Fill in the contact details the domain registration needs
- Manage DNS: sending records are handled for you, with Bulk DNS update across domains
- Optionally add a Dedicated IP, reserved exclusively for your sending infrastructure, for maximum deliverability control
Buying separate sending domains so cold email never goes out from your main domain. In Settings, open Email Infrastructure and click Create domains. Pick the mailbox product, enter your primary domain and how many you need, and Generate domains: Vetta suggests lookalikes, checks each, and shows yearly prices. Add a forwarding URL to your website and optionally a DMARC reports email, enter registration contact details, review checkout and Pay on a secure page.
Transcript
Cold email should never go out from your main domain. If those sends get flagged, your everyday email suffers too, so buy separate sending domains instead. In Settings, open Email Infrastructure and click Create domains. Pick the mailbox product they're for, then enter your primary domain and how many you need, and click Generate domains. Vetta suggests lookalike names and checks each one. Available domains show their yearly price, and you can edit or delete any of them. Click Next. Add a forwarding URL, so anyone who visits a new domain lands on your website, and, if you want them, an email for DMARC reports. Then fill in the contact details the registration needs. Checkout lists every domain with the total, and Pay takes you to a secure payment page.
The checkout lists every domain with the total, and Pay takes you to a secure payment page.
Mailboxes
Mailboxes are provisioned on your domains against your mailbox slots: every mailbox takes up one slot for as long as it exists. Buy more from the + on the Mailbox slots card: pick the type (Dedicated IP, Shared IP, Google or Microsoft), each with its own price per slot, starting from $5 a month each, then billing every 3 months or yearly (2 months free). The breakdown shows the price per slot and the total; the minimum is 10 slots, so cover the mailboxes you plan to have, not only the ones you have today. Click Subscribe to pay.
- Auto generate mailboxes across your active domains, or add them manually
- A maximum number of mailboxes per domain is enforced: concentration on one domain is a spam signal
- Configure each mailbox's signature and forwarding, so replies to sending mailboxes land in an inbox your team actually reads
Warm-up
Warm-up gradually exchanges real emails between your mailboxes and a trusted network to build sender reputation.
Starting it: click Warm-up in the page header, then Add mailbox. Any mailbox can be warmed up, not only the ones you bought here: choose Mailboxes you bought here, Google Workspace, Office 365 / Outlook, or SMTP / IMAP for any other provider. A Microsoft 365 mailbox needs Authenticated SMTP and IMAP turned on first: see Enable SMTP AUTH in Microsoft 365.
Monitoring it: the warm-up table shows each mailbox's provider, connection, Progress and Health. From a mailbox's actions, View warm up stats shows:
- Warm up emails sent
- Landed in spam: how many warm-up emails hit spam folders (falling over time is the goal)
- Inbox rate, broken down by receiving provider and by day
Placement tests show where your mail actually lands: Run placement test sends one message from the mailboxes you pick to a network of seed inboxes and reports inbox, spam or missing per provider.
Keep mailboxes warming for at least a few weeks before heavy outbound use. Adding a cold mailbox straight into a high-volume sequence is the most common self-inflicted deliverability wound.
Mailboxes can be removed from warm-up once they're carrying real sending load (Remove from warm up stops warm-up sending and does not delete the mailbox); many teams keep a low warm-up baseline running alongside outbound.
Connecting to your sequences
Once warmed, mailboxes become senders for your sequences. Deliverability discipline from there:
- Ramp up each new mailbox: start around 10 to 15 emails a day, and work up to about 30 a day per mailbox once warm-up has run its course
- Keep Global Sending Limits at the recommended values. They count per mailbox, so add warmed mailboxes when you need more volume instead of raising the limits
- Spread volume across multiple warmed mailboxes rather than maxing one
- Watch Message not sent / Delivered rates in sequence analytics, filtered by Sender: a delivery dip on one mailbox is your early warning
- Keep reply handling honest: stop on reply, honor unsubscribes: engagement signals feed reputation
Common questions
Can I warm up a mailbox I didn't buy through Vetta?
Yes. Under Warm-up, click Add mailbox and choose Google Workspace, Office 365 / Outlook or SMTP / IMAP for any other provider. A Microsoft 365 mailbox needs Authenticated SMTP and IMAP turned on first. See Warm-up.
How long should I warm up a mailbox before sending?
At least a few weeks. Putting a cold mailbox straight into a high-volume sequence is the most common self-inflicted deliverability wound. See Warm-up.
Why shouldn't I send cold email from my main company domain?
If those sends get flagged, every email your company sends is affected, including invoices and support. Use lookalike domains with a few mailboxes each. See Why separate sending infrastructure.
How do I know if my emails land in spam?
Open View warm up stats on a mailbox for Landed in spam and Inbox rate by provider, or Run placement test to see inbox, spam or missing per provider. See Warm-up.
Does removing a mailbox from warm-up delete it?
No. Remove from warm up stops the warm-up sending only, and many teams keep a low warm-up baseline running alongside outbound. See Warm-up.
How many mailbox slots do I need?
One per mailbox for as long as it exists, with a minimum of 10 slots, so cover the mailboxes you plan to have rather than only the ones you have today. See Mailboxes.
How many emails a day can a newly warmed mailbox send?
Start around 10 to 15 a day, then work up to about 30 a day per mailbox once warm-up has run its course. For more volume, add mailboxes rather than pushing one harder. See Connecting to your sequences.
How do I send more email without hurting deliverability?
Keep Global Sending Limits at the recommended values and add warmed mailboxes instead: the limits count per mailbox, so spreading volume across several is what adds capacity. See Connecting to your sequences.
Why is one mailbox delivering less than the others?
A delivery dip on one mailbox is your early warning of a reputation problem. Check Message not sent / Delivered in sequence analytics filtered by Sender and look at that account first. See Connecting to your sequences.
Key outcome
Email Infrastructure productises the deliverability playbook that agencies charge retainers for: isolated domains, managed DNS, provisioned mailboxes, and network warm-up, so by the time your sequences go live, your infrastructure already looks like a trustworthy sender.
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