The deliverability library. Every answer in one place.
Guides, short reads, help articles, and honest comparisons on email warmup, inbox placement, and cold outreach. Filter by type or search for the exact question.
Email deliverability in 2026: rule updates and the complete technical guide
Authentication mandates, AI filtering, warmup strategy, and the infrastructure non-negotiables. A complete technical guide for founders and operators running outbound.
How to start cold email outreach in 2026: a founder's playbook
Domain setup, warmup, list building, copy that beats AI filters, and the stack you actually need, in the order that matters.
AI email personalization: how to lift B2B reply rates
The conversion math, the four levels of personalization, why generic intro lines stopped working, and the deliverability constraint that gates it all.
How long does email warmup take?
21 days on the default ramp, and the measured days to 90% inbox by domain age and provider. What speeds it up and what stalls it.
Microsoft 365 emails going to junk
Microsoft's reputation-first filter, the deleted-unread signal, and how to rebuild trust.
Google Workspace emails going to spam
Gmail filters on engagement first. Spam vs Promotions, and how to win the Primary tab.
What is a warmup network?
The inbox pool behind warming, and why network quality beats network size.
What is inbox rotation in cold email?
How rotation spreads cold-email volume, and why every rotated inbox needs warming.
Does email warming help an established domain?
Warming an older domain will not lift your reply rate by itself. It lifts inbox placement, and placement decides how much of your list can reply at all.
Is your cold email tool's built-in warmup enough?
Why your tool's built-in warmup may not be enough, when it genuinely is, and how dedicated warming runs alongside any sequencer.
Should you re-warm a mailbox before sending again?
Why sender reputation decays when a mailbox goes quiet, the re-warm ramp, and how to avoid needing it.
Subdomain or separate domain for cold email?
Which one protects your main domain, the trade-offs, and why both need warming.
Cold email deliverability, measured
Where cold email lands by provider and domain age, the receivers' 2026 rules, infrastructure, warmup, content, list and monitoring.
How many cold emails per day?
The providers' caps in their words, the safe volume by domain age, the days a mailbox takes to earn it, and how many mailboxes you need.
Cold email vs email marketing: why 30 a day when marketers send millions
Two games with the same inboxes: how ESPs earn bulk volume and why cold email stays human-sized.
Do links impact email deliverability?
Short answer yes. The longer answer is about which links, how many, and where they point.
Does email warming work?
Yes, when the engagement signals look like real human behavior. The mechanism, what warmup does and does not fix, and what makes it fail.
Emails going to spam all of a sudden
The six things that change in the week before a drop, how to confirm each in minutes, and what recovery takes.
Why are my emails going to spam?
Ten causes of email landing in spam, how to diagnose which one is hitting you, and the fix for each.
Mailbox onboarding: the six settings that matter
Every warmup setting, on the screen you set it on, with what to pick.
How to warm up an email account: your first week
Setup, defaults, and what to expect in your first week.
Sender reputation score, explained
What the score is made of, who keeps one, whether it is public, how to check it at Gmail and Microsoft, and how to raise it.
Google Postmaster domain reputation
The four tiers in Google's words, why a dashboard shows no data, the study of connected domains, and the recovery steps in order.
Email warmup not working? Common issues, fixed
Score stuck, ramp not advancing, mailbox kicked offline.
SPF, DKIM, and DMARC explained
The three records receivers check first, in plain English.
How to warm up multiple domains
Warm a domain fleet in parallel, with an AI Agent per inbox, without burning any.
Gmail & Yahoo bulk sender requirements
The rules in each provider's own words, dated and linked, the enforcement timeline, the rejection codes, and a checker.
Microsoft bulk sender requirements
SPF, DKIM and aligned DMARC for 5,000 a day to Outlook.com, the 5.7.515 rejection, SNDS and JMRP, and a checker.
How to get off an email blacklist
Find the list, fix the cause, get delisted, then re-warm to recover.
How to fix a damaged sender reputation
The recovery ladder: stop the bleeding, fix the cause, re-warm at reduced volume.
What is a good open rate for cold email?
The 50% bar, why open tracking misleads, and what a Gmail-only drop means.
Is a high bounce rate hurting my deliverability?
Yes, above 2%. Hard vs soft bounces and the bounce-reputation spiral.
How to test email deliverability
Placement tests, Postmaster Tools, auth and blacklist checks, ranked by what they prove.
What is inbox placement rate?
The metric delivery rate hides, how seed lists measure it, and the 90% target.
What is a good spam complaint rate?
Stay under 0.1%, never touch 0.3%. Google's enforced thresholds explained.
Best email warmup tools (2026)
Eleven warmup tools on one table, every competitor fact from the vendor's own material, and one pick with honest caveats.
Emails going to the Promotions tab
What the tab is in Google's words, how to test for it, when to fight it, annotations for the senders who belong there, and the seed-list fix.
Newsletter deliverability
Where newsletters land by provider, the receivers' rules for bulk mail, the list and the domain, and the seed-list fix on a live issue.
Are pre-warmed domains worth it?
What is sold, what transfers with a domain or an account, Google's rules, what happens to bought accounts, and the 21 days you own.
What is an email seed list?
Real mailboxes added to a send that report where it landed per provider, and with MailStrike's seeds, act on it.
Email warmup pricing, compared
What every warmup tool costs at 10, 50 and 100 mailboxes, from each vendor's own pricing page, dated.
MailStrike vs Instantly
Bundled warmup inside an outreach platform vs. a dedicated warming engine.
MailStrike vs Lemwarm
Bundled warmup inside a sequencer vs. a dedicated engine built on agentic warmup.
MailStrike vs MailReach
Two takes on warmup quality, dashboard depth, and diagnostic tooling.
MailStrike vs Mailwarm
Warming with your own templates and expert calls vs. an AI Agent per mailbox and LLM-written threads.
MailStrike vs Warmup Inbox
12-language warmup vs. agentic warmup with content written from your company description.
MailStrike vs Warmy
All-in-one platform with 30+ language support vs. agentic warmup.
MailStrike vs Smartlead
Warmup bundled into a sending platform vs. a dedicated warming engine with AI Agents.
MailStrike vs Warmbox
A private warmup inbox pool vs. an AI Agent per mailbox and LLM-written threads.
MailStrike vs InboxAlly
Seed-based warming on mail you already send vs. two-way warming with an AI Agent per mailbox.
MailStrike vs TrulyInbox
Saleshandy's free-tier warmup partner vs. agentic warmup, placement tests and seed lists.
Blacklist removal guides
A delisting guide for every list the free blacklist checker queries. Flagged results link here too.
Reference
The lookups to keep open while you send: provider limits, bounce codes, warmup per provider and per tool.
Read enough? See where your mail lands today.
A Free Deliverability Test shows inbox, promotions, or spam per provider, with what to fix first. Or book a call and we connect a mailbox live.