Deliverability, explained by people who run the mailboxes.
Notes from the Sender Pools team on cold email infrastructure, inbox placement, and sending at scale.
How many mailboxes do you need for cold email? A sizing formula
A step-by-step formula for sizing cold email infrastructure: daily volume, safe sends per mailbox, domains per mailbox and the buffer you actually need.
Email warmup in 2026: what actually moves inbox placement
What email warmup does and does not do for cold email deliverability in 2026, how long it takes, and why it has to continue after the mailbox goes live.
Secondary domains for cold email: how to buy, configure and rotate them
Why cold email should never run on your main domain, how to choose and configure secondary domains, and how to rotate them so reputation damage stays contained.
Smartlead vs Instantly vs Sender Pools: the real cost of cold email infrastructure
What Smartlead, Instantly and Sender Pools each charge for, what you still buy separately, and how the total cost of cold email changes with volume.
A Guide To Email Preheaders - Benefits and Best Practices
What an email preheader is, why preview text lifts open rates, the ideal preheader length, and best practices for pairing preheaders with subject lines.
Cold Email Follow Up Strategies - Steps To Success
Why following up on cold emails wins most replies, how long to wait between touches, when to stop, and the rules of a cold email follow-up sequence that converts.
Cold Email Subject Lines For B2B Sales - Best Practices
How to write cold email subject lines for B2B sales that get opened: why they matter, proven formulas, mistakes to avoid and examples you can copy.
Essential Guide: Email Signature Best Practices for 2025
What to include in a professional email signature, the extras worth adding, and design best practices so your signature builds trust and stays out of spam.
How Cold Email Works
How cold email works: what makes it different from newsletters and spam, whether it is legal, the types of cold emails, and the structures that get replies.
How To Send a Video Through Email - Everything You Need To Know
Four ways to send a video through email, how to use video in newsletters and cold outreach, and tips to keep deliverability high when you embed or link video.
How to Send Bulk Cold Emails with 50%+ Open Rates
A step-by-step playbook for bulk cold emails with 50%+ open rates: list building, verification, personalization, spintax, sender rotation and sequencing.
How to Setup SPF, DKIM and DMARC For Cold Emails
How to set up SPF, DKIM and DMARC for cold email: what each record does, how to create them, whether you need both SPF and DKIM, and why DMARC can fail anyway.
How to Use Spintax for Bulk Cold Emails Effectively
What spintax is, how the {a|b|c} format and nested spintax work, why it protects deliverability, and how to use it in bulk cold email without sounding robotic.
Is Email Case Sensitive? Setting The Record Straight
Are email addresses case sensitive? What the standards say about capital letters and special characters in an address, and what it means for deliverability.
Maximizing Your Reach with Email Blasts: Strategies For Success
What an email blast is, how to set up and time a campaign, and how to measure results so bulk sends reach more inboxes without damaging your sender reputation.
P.S. In An Email: How To Use Correctly
What P.S. means, how to use a postscript in an email correctly, why it is one of the most-read lines in cold outreach, and examples you can borrow.
Prospecting vs Lead Generation: Understanding Their Differences
Prospecting vs lead generation: how the two differ, when to use each, and examples of prospecting and lead generation cold emails that fill a B2B pipeline.
Send Cold Email Without Getting Blocked
Why cold emails get blocked, how to set up your account and domains to avoid it, and how many emails you can send per day without getting blacklisted.
The Best Time To Send An Email To Cold Prospects And Boost Your Success
The best days and times to send cold emails to prospects, why timing affects open and reply rates, and what to weigh when scheduling your campaigns.
The Ultimate Guide to Overcoming Common Sales Objections
The most common B2B sales objections you'll hear after a cold email, how to categorize them, and a step-by-step process for handling and overcoming each one.
Understanding Gmail's Sending And Recipient Limits
Gmail's daily sending and recipient limits for free and Google Workspace accounts, what happens when you hit them, and how cold emailers get around them.
Using Cold Email for Lead Generation: Everything You Need To Know
How to use cold email for lead generation: build an ideal customer profile, write a message that gets replies, analyze results and optimize your campaigns.
What Affects Email Open Rates? A Deep Dive
What email open rates measure, what counts as a good average, how to calculate open rate and click-to-open ratio, and what pushes open rates up or down.
Writing Effective Cold Email Messages: Everything You Need To Know In 2025
How to write effective cold emails in 2025: why they still work, a five-step process from research to subject lines, and answers to common cold email questions.
It's nicer here. Jump in!
Join thousands of cold emailers that send on Sender Pools.
Sign upGet started for $20→