Guides
Everything about setting up and running cold email infrastructure, in plain English, with sources.
Guides
How to Keep Cold Emails Out of the Spam Folder
Cold emails land in spam when receiving servers cannot verify you (missing SPF, DKIM or DMARC), when your domain or mailbox has no sending history or a bad one, when you send too much too fast, when your list bounces or draws complaints, or when tracking links and spammy formatting make the message look like bulk mail. Fix them in that order: authenticate a separate sending domain, warm up every mailbox, keep volume low per mailbox, verify your list, and send short plain-text emails with tracking turned off or on a custom tracking domain. No setup guarantees the inbox, but these steps remove the most common reasons for the spam folder.
7 min read
Gmail, Yahoo and Microsoft bulk sender requirements explained
Since February 2024, Gmail and Yahoo require anyone sending about 5,000 or more messages a day to their users to pass SPF and DKIM, publish a DMARC record (p=none is enough) that aligns with the From domain, offer one-click unsubscribe (RFC 8058) on marketing and subscribed mail, and keep the user-reported spam rate below 0.3%. Since May 5, 2025, Microsoft requires domains sending more than 5,000 messages a day to Outlook.com, Hotmail and Live addresses to pass SPF, DKIM and DMARC, and rejects non-compliant mail with error 550 5.7.515. All senders to Gmail also need SPF or DKIM, valid reverse DNS, TLS and a spam rate below 0.3%.
8 min read
How to buy domains for cold email (names, TLDs, forwarding)
Buy secondary domains that clearly resemble your brand, such as getacme.com, tryacme.com or acmehq.com, and send cold email only from those, never from your main domain. Choose .com where possible and avoid very cheap TLDs that are heavily used for spam. Forward each domain to your main website, and buy enough for 2–3 mailboxes per domain plus a few spares.
6 min read
How Much Does Cold Email Infrastructure Cost? (2026)
As of October 2026, the biggest cost in cold email infrastructure is mailbox seats: Google Workspace Business Starter lists at $7 per user per month on an annual plan ($8.40 on the monthly Flexible plan), and Microsoft 365 Business Basic lists at $7 per user per month with an annual commitment. Add sending domains (roughly one for every two or three mailboxes, about $13 a year each through ReplyDak), a sequencer such as Instantly or Smartlead (from about $39 to $47 a month on their entry plans, which include warmup), and your setup time. For 30 mailboxes, a do-it-yourself setup on Google Workspace list prices costs about $221–$263 a month before the sequencer; a managed provider like ReplyDak costs $87 a month for 30 mailboxes plus domains.
7 min read
How to set up cold email infrastructure (step by step, 2026)
To set up cold email infrastructure, buy a few secondary domains that look like your brand, point their DNS to a provider you control, and create 2–3 mailboxes per domain on Google Workspace or Microsoft 365. Publish SPF, DKIM and DMARC records for every domain, warm each mailbox up for about three weeks, then connect the mailboxes to a sequencer such as Instantly or Smartlead and keep each one to roughly 30–50 cold emails a day. Never send cold email from your main company domain.
9 min read
How many cold emails can you send per day per mailbox?
For cold outreach, send about 30 emails per mailbox per day and no more than about 50, counting follow-ups. Provider hard limits are much higher (Google Workspace allows 2,000 messages per user per day, or 500 on trial accounts; Exchange Online allows 10,000 recipients per day), but those are for normal business mail, and cold email sent near them gets filtered. To send more, add mailboxes and domains instead of raising the per-mailbox number.
6 min read
How to Connect Google Workspace Mailboxes to Instantly and Smartlead
There are two ways to connect Google Workspace mailboxes to Instantly or Smartlead. OAuth: a Workspace admin marks the sequencer's app as trusted in the Google Admin console, then each mailbox signs in with Google and clicks Allow. IMAP/SMTP: each mailbox turns on 2-Step Verification, creates an app password, and you enter it with Gmail's IMAP and SMTP server settings, either one by one or in bulk through the sequencer's CSV import. OAuth is quicker for a few mailboxes you administer; CSV bulk import is faster for dozens, and ReplyDak exports a ready-made CSV in Instantly's and Smartlead's import formats.
7 min read
Email Deliverability Checklist for a New Outbound Program
Before you send the first cold email, confirm five things: you send from separate domains (not your main one), every domain passes SPF, DKIM and DMARC, every mailbox has been warmed up for about three weeks, your list is verified, and your sequencer is set to low daily volume with tracking off or on a custom tracking domain. Then plan how you will monitor bounces, replies and spam complaints and when you will pause. The table and steps below turn this into a checklist you can tick off.
7 min read
Google Workspace for cold email: DIY or managed provider?
You can buy Google Workspace seats from Google, set DNS records and warm mailboxes up yourself; it works, but expect several hours of setup per batch of domains, a separate warmup tool, and full responsibility when something breaks. A managed provider does the same steps in minutes, at a per-mailbox price close to Google's own list price, with DNS, warmup and sequencer exports included. DIY makes sense for a handful of mailboxes or strict in-house control; past about 10 mailboxes most teams save time and money with a provider.
7 min read
Google Workspace vs Microsoft 365 for cold email
Both Google Workspace and Microsoft 365 work for cold email; the best choice usually depends on what your prospects use. Google Workspace is the default for most teams because it is simple to set up and automate, while Microsoft 365 mailboxes are worth adding when a large share of your list is on Microsoft (common with enterprises and some regions). Check prospects' MX records, split your list by provider, and test both on the same campaign.
6 min read
How many mailboxes per domain for cold email?
Use 2–3 mailboxes per sending domain for cold email. Each mailbox sends about 30 (at most 50) cold emails a day, so a domain carries roughly 60–150 emails a day, and you scale by adding domains rather than stacking more mailboxes on one domain. For example, 600 emails a day needs about 20 mailboxes on 7–10 domains.
5 min read
Why You Should Never Cold Email From Your Main Domain
Never send cold email from your company's main domain, because spam complaints, bounces and blocklistings attach to the domain, and a damaged main domain can push your everyday email, invoices, password resets and support replies into spam too. Instead, register a few lookalike domains (for example getacme.com or acmehq.com for acme.com), authenticate them with SPF, DKIM and DMARC, forward them to your main website, and send cold outreach only from mailboxes on those domains. Use a custom tracking subdomain on a sending domain, or no tracking, so your main domain never appears in tracked links.
6 min read
SPF, DKIM and DMARC for cold email: exact records and checks
Every cold email domain needs three DNS TXT records: one SPF record that authorises your mail provider (for Google Workspace `v=spf1 include:_spf.google.com ~all`), a DKIM public key generated in your provider's admin console, and a DMARC record at `_dmarc.yourdomain.com` such as `v=DMARC1; p=none; rua=mailto:reports@yourdomain.com`. Gmail, Yahoo and Outlook.com require all three for high-volume senders, and DMARC only passes when the From domain aligns with the SPF or DKIM domain. Check them by sending a test email and reading the Authentication-Results header.
7 min read
How to warm up a new email domain for cold email
Warm up a new domain by sending a small, slowly rising number of emails from each mailbox that get opened and replied to, starting around 2–5 a day and reaching about 30 a day over roughly three weeks, before you start cold campaigns. Keep warmup running at a lower level after campaigns start, and slow down if bounces or spam placement rise. Warmup builds a sending history; it cannot fix bad lists, irrelevant copy or high complaint rates.
6 min read
Comparisons
Best cold email infrastructure providers (2026 buyer's guide)
The best cold email infrastructure provider is the one that sells the mailbox type you want (real Google or Microsoft seats, the provider's own SMTP, or Microsoft tenants), lets you own your domains, automates DNS and warmup, and fits your volume and billing needs. For Google Workspace mailboxes at a low monthly price, ReplyDak, Inboxkit and Zapmail lead; for Microsoft 365 today, Zapmail, Inboxkit and Primeforge; for the lowest cost at very high volume, own-infrastructure providers such as Maildoso.
8 min read
ReplyDak vs Inboxkit: Google Workspace mailbox pricing compared
Inboxkit charges $3 per Google or Microsoft mailbox monthly, or $2.50 if you pay for a year, and sells an Azure tenant at $30 a month for up to 100 mailboxes. ReplyDak charges $3.50, $2.90 or $2.69 per Google Workspace mailbox on monthly billing, with warmup included. Inboxkit is cheaper at 10 mailboxes, on annual billing and for Microsoft; ReplyDak is cheaper on monthly billing from 30 mailboxes up and bills in INR with a GST invoice.
6 min read
ReplyDak vs Mailforge (and Primeforge): which to choose
Mailforge is not Google Workspace or Microsoft 365: it runs mailboxes on Salesforge's own infrastructure with a shared IP pool, at $3 per slot. Primeforge, its sister product, sells real Google and Microsoft mailboxes at $4.50 per slot. ReplyDak sells real Google Workspace mailboxes at $2.69–$3.50, so it costs less than Primeforge for the same mailbox type and is close to Mailforge's price while sending from Google's servers.
6 min read
ReplyDak vs Zapmail: price, features and which to pick
ReplyDak is cheaper than Zapmail at every plan size ($35 vs $39 for 10 mailboxes, $87 vs $99 for 30, $269 vs $299 for 100), includes warmup, and bills in INR with a GST invoice. Zapmail is the better pick if you need Microsoft 365 mailboxes today, pre-warmed mailboxes, an API or built-in placement tests, none of which ReplyDak offers yet. Both sell real Google Workspace mailboxes on your own domains.
6 min read
Best Zapmail alternatives (2026)
The closest Zapmail alternatives are providers that also sell real Google Workspace or Microsoft 365 mailboxes: ReplyDak ($2.69–$3.50 per mailbox), Primeforge ($4.50), Inboxkit ($3, or $2.50 billed yearly), Premium Inboxes and Cheap Inboxes ($3.50 down to $2.80). If you want the lowest price and accept a non-Google, non-Microsoft sending stack, Mailforge ($3 per slot, shared IPs) and Maildoso ($2.50 down to $0.49, its own SMTP) cost less. Pick by mailbox type first, then price, then features such as API access and pre-warmed mailboxes.
7 min read
Use cases
Cold Email for Indian IT Services and SaaS Companies Selling Abroad
Indian IT services and SaaS companies selling to the US and Europe should send outbound from separate, authenticated lookalike domains with warmed Google Workspace mailboxes, schedule emails for the prospect's morning (roughly 6:30–8:30 pm IST for the US East Coast and 1:30–3:30 pm IST for the UK and central Europe, depending on daylight saving), and write short, specific emails that show relevant work rather than long capability lists. Follow CAN-SPAM for US prospects and GDPR (plus national rules such as the UK's PECR) for European ones. ReplyDak can bill in INR with a GST invoice, so the cost is booked like any other Indian business expense.
8 min read
Cold Email Infrastructure for Lead Gen and Marketing Agencies
Agencies running outbound for several clients should give every client its own set of sending domains and mailboxes, never shared between clients, so one client's list or offer cannot damage another client's deliverability. Size each client at about one warmed mailbox per 30 emails a day with 2–3 mailboxes per domain, keep warmed spares for new clients, and report per client on replies and meetings rather than opens. Cost is mostly mailboxes: at ReplyDak's Scale price of $2.69 per mailbox, a client running 20 mailboxes costs about $54 a month plus domains.
7 min read
Cold Email Infrastructure for Recruiting and Staffing Agencies
Recruiting and staffing agencies should run two separate outbound streams, client business development and candidate outreach, each on its own lookalike sending domains so a problem in one never affects the other or your main agency domain. Plan about one warmed mailbox per 30 emails a day: a recruiter sending 150 candidate emails a day needs around 5 mailboxes on 2 domains. Keep messages personal and short, honour opt-outs quickly, and check privacy and anti-spam rules (such as CAN-SPAM in the US and GDPR in the EU and UK) for every country you contact.
7 min read
Cold email infrastructure for SaaS startups
A SaaS startup doing outbound needs separate sending domains, about one warmed mailbox per 30 emails a day, and a sequencer, so 300 emails a day means roughly 10 mailboxes on 4–5 domains. Founder-led outbound usually starts with 3–10 mailboxes; an SDR team typically runs 10–20 per rep. Measure positive replies and meetings booked per 100 prospects, not opens, and keep your main product domain out of cold sending.
7 min read