Practical guides on infrastructure, deliverability, warmup, and scaling outbound — from the Inboxlogy team.
Warm a new cold email domain for 2–4 weeks before real sending, keep each mailbox under roughly 20–40 cold emails per day, and rotate volume across many mailboxes rather than pushing any single one harder. Warmup runs in
To warm up a cold email inbox: get SPF, DKIM and DMARC passing first, let the domain sit for 7–14 days, then connect each mailbox to the warmup pool inside your sending tool (Instantly, Smartlead, ReachInbox). Start at 2
Check three things: the mailbox's actual sending history (not just days-since-creation), real inbox placement test results across providers, and SPF/DKIM/DMARC alignment on the sending domain. If a seller can't show you
Send 20–30 cold emails per day per mailbox on a fully warmed, dedicated sending domain. For the first two to three weeks of a new mailbox's life, send 10–15 per day. The technical ceilings are far higher (Google Workspac
Once SPF, DKIM, and DMARC are published and propagated, the checklist is: verify DNS with a live test email, create mailboxes with real-looking names and matching signatures, set up forwarding/profile photos, connect eac
You cannot buy sender reputation. What sellers call a "pre-warmed email account" is a mailbox on a domain someone else registered and ran through a warmup pool. That warmup history belongs to the domain and the tenant, n
Warm new cold email domains for 2-4 weeks before sending. Cap each mailbox at 20-35 sends/day. Use 2-3 mailboxes per domain. For 10,000 prospects/month, you need ~40 mailboxes across ~14 domains. Never use your primary d
The best alternatives to Instantly for cold email mailboxes are providers that sell you mailboxes you actually own and administer: authorized Google Workspace / Microsoft 365 mailbox providers (Inboxlogy, Zapmail, Mailsc
Buy from an authorized reseller if you need more than about 10-15 mailboxes, multiple sending domains, or you value your time. Reseller pricing is usually below Google's list price and the DNS, DKIM and tenant work is do
Microsoft 365 mailboxes for cold email come from four places: Microsoft directly, authorized CSP (Cloud Solution Provider) resellers, cold email infrastructure companies that provision tenants and domains for you (Inboxl
There is no single best cold email infrastructure provider for everyone. There is a clear best category: providers that give you mailboxes on authorized Google Workspace or Microsoft 365 tenants that you own outright, wi
A cold email inbox is a dedicated, fully authenticated mailbox on a secondary domain, used to send a deliberately small daily volume of outbound email, typically 20–40 sends per mailbox per day, with 2–3 mailboxes per do
For most B2B cold email programs the right answer is both: match the mailbox provider to the prospect's mail host, sending to Google-hosted domains from Google Workspace mailboxes and Microsoft-hosted domains from Micros
Agencies avoid burning domains by spreading sending across many cheap secondary domains instead of one. The usual shape is 2–3 mailboxes per domain, 20–40 emails per mailbox per day, on fully authenticated, provider-auth
If your domains are registered in your name at a registrar you can log into, and your mailboxes live in a Google Workspace or Microsoft 365 tenant where you hold the super admin / global admin account, then yes, you own
Cold email ROI = (gross profit from closed deals − fully loaded campaign cost) ÷ fully loaded campaign cost. In most B2B cases the cost side is small and nearly fixed. Mailboxes, data, tooling, and operator time typicall
Agencies avoid burned domains by making the domain disposable and the volume invisible: they send from cheap secondary domains that carry no business value, put only 2–3 mailboxes on each domain, cap each mailbox at roug
Cold email infrastructure typically costs $0.01–$0.03 per email sent, which works out to roughly $75–$200/month for a solo sender (250 emails/day), $650–$1,200/month for a scaling team (2,500 emails/day), and $2,000–$4,0
The cheapest legitimate way to get 100 Google Workspace inboxes for cold outbound is to buy them through an authorized Workspace reseller or infrastructure provider on month-to-month billing, roughly $2.80–$4 per mailbox
Cheap cold email inboxes cost roughly $1-$4 per mailbox per month. The cheapest option that is actually safe to build a pipeline on is an authorized Google Workspace or Microsoft 365 mailbox that you own outright, with y
Buy Google Workspace seats on alternate domains you own, roughly 2–3 mailboxes per domain and one mailbox per ~30 sends/day. Two routes work: direct from Google (one tenant, many secondary domains), or through an authori
To authenticate a cold email domain you need three DNS records on that domain: one SPF TXT record listing your sending provider (v=spf1 include:_spf.google.com -all for Google Workspace, include:spf.protection.outlook.co
The fastest way to check is to look at your mailbox or SMTP provider's admin settings or billing page for a line that says "dedicated IP," "static IP," or shows an IP address tied only to your account. If you can't find
Automate it in three layers. Put every domain's DNS behind one API-capable provider (Cloudflare is the pragmatic choice), define SPF/DMARC/MX as code with DNSControl or Terraform, and script DKIM key generation per mailb
In short: An MX (Mail Exchange) record tells the internet which servers receive email for your domain, and in what order to try them. The lowest priority number is tried first. Without a valid MX record, your domain simp
In short: The best cold email signature is short, text-based and human. Include your name, role, company and one link. Cut images, tracking pixels, social icon rows and long disclaimers. A heavy signature hurts your text
In short: To check DKIM, open a free DKIM Checker, enter your domain and your selector, and it looks up the public key at selector._domainkey.yourdomain.com. If you do not know your selector, the tool tries common ones (
In short: To analyze an email header: open the message, find 'Show original' or 'View source', copy the raw text, and paste it into a free Email Header Analyzer. It decodes the SPF, DKIM and DMARC results, the server hop
In short: To check DMARC, open a free DMARC Checker, enter your domain, and read the result. It finds the record at _dmarc.yourdomain.com, tells you your policy (none, quarantine or reject) in plain English, and flags if
In short: DKIM adds a cryptographic signature to every email you send. Your mail server signs messages with a private key, and mailbox providers verify the signature using a public key you publish in DNS. A valid DKIM si
In short: The three DMARC policies control what happens to mail that fails authentication. p=none monitors only and changes nothing. p=quarantine sends failing mail to spam. p=reject blocks it entirely. Start at none, co
In short: To check your SPF record, open a free SPF Checker, enter your domain, and read the result. It shows your full record, whether the policy is a soft or hard fail, and your DNS lookup count against the limit of 10
In short: To create an SPF record, list every service that sends mail for you, combine them into one v=spf1 record with include: statements, and end with ~all or -all. A free SPF Generator builds this for you and keeps y
In short: To create a DMARC record, publish a TXT record at _dmarc.yourdomain.com starting with v=DMARC1, a policy (p=none to begin), and a reporting address. A free DMARC Generator builds the exact string. Roll out slow
In short: To check a domain's DNS records, open a free DNS Record Checker, type the domain, and read the results. It queries live public DNS over secure DNS-over-HTTPS and returns the A, AAAA, MX, TXT, NS and CNAME recor
In short: To set up BIMI: confirm your DMARC is at quarantine or reject, prepare an SVG P/S logo, generate the record with the free BIMI Generator, decide whether you need a VMC, then publish the TXT record at default._b
In short: To set up DKIM, generate a key pair: a private key that stays on your mail server and a public key you publish in DNS at selector._domainkey.yourdomain.com. A free DKIM Generator creates a 2048-bit pair entirel
In short: DKIM uses a key pair. The private key signs your outgoing mail and lives only on your mail server. The matching public key is published in DNS so receivers can verify the signature. A selector labels each key s
In short: To check for a blacklisting, enter your sending IP or domain into a free Blacklist Checker. It queries major DNSBLs and shows which list you, if any. If you are listed, fix the cause first, then request delisti
In short: To run an MX lookup, open a free MX Lookup tool, enter the domain, and read the mail servers it returns in priority order. The tool also detects the email provider automatically, so you instantly know whether a
In short: An SPF record is a line in your DNS that lists which servers are allowed to send email for your domain. When a mailbox provider receives your mail, it checks the sending server against this list. If the server
In short: A correct SPF record is one v=spf1 line that lists all your senders and ends in a policy. For Google Workspace it is v=spf1 include:_spf.google.com ~all; for Microsoft 365 it is v=spf1 include:spf.protection.ou
In short: A DMARC record tells mailbox providers what to do when an email claiming to be from your domain fails SPF and DKIM, and where to send reports. Its policy is set by the p= tag: none (monitor only), quarantine (s
In short: DNS records are the public instructions that tell the internet how to route and trust your domain. For email, six matter most: MX (where mail is received), A/AAAA (your server addresses), and the TXT-based SPF,
In short: BIMI (Brand Indicators for Message Identification) displays your brand logo next to your emails in supporting inboxes like Gmail and Apple Mail. To use it you need DMARC at quarantine or reject, a logo in a spe
Cold email deliverability is the probability that an unsolicited outbound email reaches the recipient's inbox rather than spam, quarantine, or a silent block. Three things you control decide most of it: authenticated, pr
Cold email deliverability is the share of your cold emails that land in the recipient's primary inbox instead of bouncing or being filtered to spam. Four levers control it, in order of impact: correctly authenticated inf
Cold email deliverability comes down to four things: authenticate every sending domain with aligned SPF, DKIM, and DMARC; send from mailboxes you genuinely own on authorized Google Workspace or Microsoft 365 tenants; kee
To improve cold email deliverability, send from separate sending domains with correctly aligned SPF, DKIM, and DMARC, keep each mailbox under roughly 20-40 sends per day, verify your list so bounces stay under 2-3%, turn
Cold email deliverability in 2026 comes down to five things: send from separate domains you fully own with SPF, DKIM, and DMARC aligned; keep per-mailbox volume low and engagement high; strip tracking pixels and link sho
In short: A new domain has no sending reputation, so blasting cold email on day one looks like spam and gets you filtered or blacklisted. Warming up means ramping volume gradually over several weeks so mailbox providers
In short: An email blacklist (or DNSBL) is a public list of IP addresses and domains known for sending spam. Mailbox providers check these lists before accepting mail, so being listed can send your email straight to spam
In short: Spam trigger words are terms and phrases long associated with junk mail ("free money", "act now", "guaranteed"). Modern filters care less about any single word and more about patterns: too many triggers, ALL CA
In short: An email header is the hidden metadata at the top of every message. It records the path the email took, the authentication results (SPF, DKIM, DMARC), timestamps and server names. Reading it tells you exactly w
In short: To reduce bounces: verify addresses before sending, decode every bounce to separate hard from soft, remove hard bounces immediately, warm up new domains, and keep authentication clean. A high bounce rate wrecks
In short: A bounce is an email that could not be delivered. A hard bounce is permanent (the address does not exist) and you must stop mailing it. A soft bounce is temporary (mailbox full, server busy) and may succeed on
In short: Your warm-up schedule should start low (around 20-40 a day), increase gradually each week, and reach full volume over three to six weeks. The exact daily numbers depend on your target. The free Warm-Up Calculat
In short: Staying out of spam comes down to five things: authenticate (SPF, DKIM, DMARC), warm up new domains, send to clean lists, write human copy, and test before you scale. No single trick fixes placement; these work
The best way to verify cold email addresses is a layered pipeline: strip syntax errors and disposable domains, confirm the domain has live MX records, run an SMTP-level check through a reputable third-party verifier, and
Use 1 mailbox per 20-30 daily sending slots you need, rotate sends evenly across all mailboxes in the pool, cap each mailbox at 15-25 emails per day, and keep total daily volume per domain under 50-60 emails. For most B2
Agencies avoid burned domains by spreading volume thin instead of stacking it: 2-3 mailboxes per domain, 20-40 cold sends per mailbox per day, a separate domain pool per client, and authorized Google Workspace or Microso
For most cold email programs, a dedicated sending IP is not what gets you into the inbox. Domain reputation, authentication, and list quality are. A dedicated IP matters in two specific situations: when you send high, st
In short: To schedule across time zones, work from the recipient's local time, not yours. Find their timezone, target mid-morning on a weekday there, and schedule the send accordingly. The free Best Time to Send tool sho
In short: A good email signature is simple: name, title, company, one phone number, and a link. Build it with a free Email Signature Builder, keep it lightweight, and avoid heavy images or spammy banners. For cold email
In short: Accessible email can be read by everyone, including people using screen readers or with low vision, and it tends to perform better for all recipients. The essentials: alt text on images, strong colour contrast,
In short: The best time to send cold email is generally mid-morning on a weekday in the recipient's own timezone, when they are at their desk but not buried. Tuesday to Thursday tends to beat Monday and Friday. But timin
In short: To preview your email on mobile, paste its HTML into a free Mobile Email Preview tool. It renders your message inside a phone-sized frame so you can see small text, overflowing images and hard-to-tap links befo
In short: To make an email accessible: add alt text to images, ensure strong contrast, use a readable font size, and structure content with real headings. Then verify with the free Accessibility Checker, which flags what
In short: More than half of all email is opened on a phone, so if your message breaks on mobile, most recipients see the broken version. Tiny text, cut-off images, untappable links and awkward layouts all cost replies. P