Resource

📤 The Complete Guide to Email Deliverability

4/15/2025

by Sara McNamara

A comprehensive, practical template to help improve and maintain inbox placement for marketing, sales, and transactional emails.

📬 But Sara….What Is Email Sending Reputation?💡 Best Practices to Maintain a Good Sending Reputation SECTION 1: DOMAIN AUTHENTICATION & COMPLIANCE SECTION 2: INFRASTRUCTURE & SENDING STRATEGY SECTION 3: LIST QUALITY & SENDER REPUTATION SECTION 4: EMAIL CONTENT & DESIGN SECTION 5: MONITORING & ONGOING OPTIMIZATION 🧪 BONUS: WARM-UP PLAN FOR NEW DOMAINS/IPs*📈 Email Warm-Up Schedule ☑️ Email Deployment Checklist 📄 Helpful Additional Cheat Sheets List of all freemium email domains: https://gist.github.com/Artistan/9662757 List of email malformations I typically filter for:Typical throwaway email domains:✍️ Enterprise Pro Tips

📬 But Sara….What Is Email Sending Reputation?

Email sending reputation is a score that mailbox providers (like Gmail, Outlook, Yahoo, etc.) assign to your IP address and domain based on how recipients interact with your emails. A strong reputation increases your chances of landing in the inbox; a poor one can send your emails straight to spam…or block them entirely.

💡 Best Practices to Maintain a Good Sending Reputation

Area	Best Practice
Authentication	Set up SPF, DKIM, and DMARC for your domain
Consistent Volume	Avoid large spikes in email volume — warm up gradually
Engagement Monitoring	Regularly monitor opens, clicks, bounces, and spam complaints
List Hygiene	Clean your list frequently and remove inactive or bounced emails
Opt-In Practices	Use double opt-in and never buy or scrape email lists
Avoid Spam Triggers	Watch subject lines, avoid all caps, misleading language, or image-only emails
Feedback Loops	Set up complaint feedback loops with providers like Yahoo and Microsoft
Monitor Reputation	Use tools like Google Postmaster Tools and Talos Intelligence

SECTION 1: DOMAIN AUTHENTICATION & COMPLIANCE

Proper domain authentication is non-negotiable for inbox placement. If you don’t have these set up, you risk being sent straight into the spam folder.

The way I like to explain this to clients: this is like running up to someone in a cafe and asking them to send your invitations to all of their friends. If you run up without introducing yourself, you’ll likely scare the person and they’ll throw most of your invites in the trash; if you introduce yourself, show ID, and build credibility, your invitations are more likely to send up being sent properly. It’s all about seeing a good first impression!

Item	Why It Matters	How to Check / Fix	Tools	Educational Resources
SPF	Tells receiving servers which senders are allowed to send on your behalf	Add a TXT record in your DNS zone	MXToolbox SPF, Google SPF Guide	What is a DNS SPF record? \| Cloudflare What is a DNS SPF record? \| Cloudflare A sender policy framework (SPF) record is a type of DNS TXT record that lists all the servers authorized to send emails from a particular domain. A DNS TXT (“text”) record lets a domain administrator enter arbitrary text into the Domain Name System (DNS)
DKIM	Adds a digital signature proving the message was authorized and unmodified	Set up in your ESP and publish DNS record	ㅤ	What is a DNS DKIM record? \| Cloudflare What is a DNS DKIM record? \| Cloudflare A DKIM record is a specialized DNS TXT record that stores the public key used to verify an email's authenticity. Learn how DKIM lookups work.
DMARC	Aligns SPF & DKIM and tells mailbox providers what to do with unauthenticated mail	Start with `p=none` and monitor reports	DMARC Analyzer, Valimail Setup	FortinetWhat Is DMARC? How Does DMARC Work? \| Fortinet What Is DMARC? How Does DMARC Work? \| Fortinet DMARC is short for Domain-based Message Authentication, Reporting, and Conformance. DMARC is an email security protocol that verifies email senders by supporting email protocols like DNS, DKIM, and SPF. Fortinet
BIMI	Enables logo display in inboxes (ex. Gmail, Yahoo)	Requires DMARC + VMC Certificate	BIMI Group, Gmail BIMI Guide	postmarkappWhat the heck is BIMI and why is it so important? What the heck is BIMI and why is it so important? BIMI (or Brand Indicators for Message Identification) is critical for email deliverability. We explain what it is and how to enable it for your email messages. postmarkapp

SECTION 2: INFRASTRUCTURE & SENDING STRATEGY

These are foundational elements to separate your good messages from spammy traffic.

If you want to work to ensure you have great inbox placement, look here to set further foundation.

Item	Why It Matters	How to Check / Fix	Tools	Educational Resources
Use a Custom Subdomain	Isolates sender reputation	Configure in DNS & ESP	ㅤ	MailgunThe Basics of Subdomains and How To Use Them \| Mailgun The Basics of Subdomains and How To Use Them \| Mailgun Get the scoop on what email subdomains are and how to properly use them. Read more... Mailgun
Dedicated IP	Full control over IP reputation	Set up via ESP if >100K emails/month	ㅤ	MailchimpDedicated IP: The Key to Maximizing Email Deliverability \| Mailchimp Dedicated IP: The Key to Maximizing Email Deliverability \| Mailchimp Ensure the deliverability of your emails with a dedicated IP address. Learn more about what dedicated IPs for email marketing are and how to use one. Mailchimp
Reverse DNS (rDNS/PTR)	Required by most providers	Should match sending domain	GlockApps SMTP Test	MailGeniusEmail Deliverability Checklist: Proven 13-Step Inbox Placement List Email Deliverability Checklist: Proven 13-Step Inbox Placement List Discover our comprehensive 13-step Email Deliverability Checklist. Learn proven strategies for boosting your inbox placement rate. MailGenius
TLS Encryption	Secures email delivery	Confirm with ESP	SSL Labs Test	Egress Software TechnologiesTLS email encryption: What you need to know \| Blog \| Egress TLS email encryption: What you need to know \| Blog \| Egress TLS is the dominant encryption protocol for protecting email contents. Find out everything you need to now about TLS email encryption in our latest guide. Egress Software Technologies

SECTION 3: LIST QUALITY & SENDER REPUTATION

This is where most issues originate. Poor list hygiene = poor inboxing.

It’s not enough to set the foundation — your email sender reputation is something that has to be taken care of and tracked, month over month.

Item	Why It Matters	How to Check / Fix	Tools	Educational Resources
Double Opt-In	Verifies intent and reduces bounces	Configure in ESP	Typically available in most email service providers	WPFunnelsUnderstanding Double Opt-in Email - A Comprehensive Guide [2024] Understanding Double Opt-in Email - A Comprehensive Guide [2024] One of the best ways to maintain email list quality is by using a double opt-in email strategy. Learn how and when to use double opt-in emails effectively. WPFunnels
Clean Lists Regularly	Removes bounces, traps, inactives	Clean quarterly or monthly	ZeroBounce, NeverBounce, internal resources like data analysts	MailchimpCleaning Email Lists 101: Refreshing Address Lists \| Mailchimp Cleaning Email Lists 101: Refreshing Address Lists \| Mailchimp Learn how to scrub your email list. Regular email cleaning benefits your email marketing strategy and can improve metrics like conversion and open rates. Mailchimp
Suppress Unengaged	Reduces risk of spam placement	No opens/clicks in 90+ days	Use ESP segmentation	Example of unengaged suppression in HubSpot: community.hubspot.com community.hubspot.com
Monitor Complaints & Bounces	High rates damage sender score	Review post-send dashboards	Google Postmaster, Postmark	10 Email Deliverability Monitoring Practices for Email Success 10 Email Deliverability Monitoring Practices for Email Success Discover 10 must-have tips from experts on how to reach every inbox and maximize ROI by regularly monitoring your email deliverability. From Inbox to Impact.

SECTION 4: EMAIL CONTENT & DESIGN

Good content doesn’t just look good, it also impacts inboxing.

If you do all of the things above but are sending junky content, you’ll end up in the Promotions or Spam folder.

Item	Why It Matters	How to Check / Fix	Tools	Educational Resources
Avoid Spammy Subject Lines	Prevents spam triggers	Avoid ALL CAPS, misleading text	Many ESPs have this within their preview functionality	MailGeniusSpammy Subject Lines Exposed: Safeguard Your Email Reputation Spammy Subject Lines Exposed: Safeguard Your Email Reputation Discover the hidden risks of spammy subject lines and take action to protect your email reputation. Learn how to avoid common pitfalls. MailGenius
Alt Text & Mobile Optimization	Improves accessibility	Use responsive HTML; avoid image-only	Litmus	HubSpotMobile Email Optimization: A 5-Step Guide Mobile Email Optimization: A 5-Step Guide Nearly half of all emails are opened on mobile devices. Stop missing opportunities with these tips for optimizing your email marketing. HubSpot
Plain-Text Version	Boosts inbox placement	Auto-generated, but review manually	Mail Tester	MailmodoHTML vs Plain Text Emails: Which One to Choose and Why? HTML vs Plain Text Emails: Which One to Choose and Why? This guide compares HTML and plain text emails and helps you make a more informed and data-driven decision about which one to choose. Mailmodo
Test Before Sending	Detect spam, render issues	Send to seed list or spam checker	GlockApps, Mail Tester	☑️ Email Deployment Checklist

SECTION 5: MONITORING & ONGOING OPTIMIZATION

Inbox placement is a moving target. These tools help you stay ahead.

BTW: Gmail and the other ESPs continue to make updates, email is not something you just “set and forget.” These tools and practices will help you stay on top of the latest.

Item	Why It Matters	How to Check / Fix	Tools	Educational Resources
Google Postmaster Tools	View Gmail reputation, delivery issues	Connect your domain	Google Postmaster	MicrosoftLearnGoogle Postmaster Tools - What it's and how it can help you - Dynamics 365 Customer Insights Google Postmaster Tools - What it's and how it can help you - Dynamics 365 Customer Insights Learn how to use Google Postmaster Tools to gain delivery insights in Dynamics 365 Customer Insights - Journeys. MicrosoftLearn
Feedback Loops	Get notified of spam complaints	Most ESPs have this built-in	ㅤ	MailgunFeedback Loops and Spam Complains Feedback Loops and Spam Complains Best Practices <Product>. Mailgun
Inbox Placement Testing	Know where your email lands	Test monthly or pre-campaign	Email on Acid, GlockApps	MailtrapInbox Placement Explained [2025] Inbox Placement Explained [2025] Inbox placement should concern you even more than email deliverability! Learn what inbox placement is, how it works, how to calculate inbox placement rate, and how to improve the metric! Mailtrap
Blacklist Monitoring	Avoid global blocklists	Monitor weekly	MXToolbox Blacklist	Email Blacklist: Causes, Impact, And How To Check It Fast Email Blacklist: Causes, Impact, And How To Check It Fast What is an email blacklist check? Is my email blacklisted? This article provides answers and explains how to remove your email address from blacklist.

🧪 BONUS: WARM-UP PLAN FOR NEW DOMAINS/IPs*

*This also applies if you’re moving domains or migrating tools!

Week 1: Send to 100–500 highly engaged, ideally validated email address contacts/day

Week 2: Scale to 1,000–2,000/day, mixing in newer segments

Week 3+: Double volume weekly until fully ramped

Pro Tip: Start with engagement-based segments to build trust.

📈 Email Warm-Up Schedule

Remember, this is not only for when you first start a new email program — this also applies for any major changes, like marketing automation or sales automation platform migration.

Week	Daily Volume	Audience Description	Notes
Week 1	100–500/day	Highly engaged, validated email addresses	Use only contacts with high open/click rates
Week 2	1,000–2,000/day	Mix of engaged + newer segments	Begin slowly expanding to colder but opted-in leads
Week 3	2,000–4,000/day	Expand to broader active list	Continue to monitor engagement + bounce rates
Week 4	4,000–8,000/day	Include newer leads and larger segments	Gradually introduce less-tested segments
Week 5	8,000–16,000/day	Most of your email list	Monitor domain/IP reputation closely
Week 6+	Full list (based on cap)	Entire subscriber base	Full sending volume if reputation is stable

☑️ Email Deployment Checklist

Copy + paste this and add in your own unique steps for your business!

Category	Item	Description	Owner	Status	Notes
Strategy	Audience Segment Confirmed	Correct list or segment selected	ㅤ	☐	ㅤ
ㅤ	Send Goal Confirmed	Promotional, nurture, transactional, etc.	ㅤ	☐	ㅤ
ㅤ	Suppression Lists Applied	Exclude unsubscribed, unengaged, internal, or recent recipients	ㅤ	☐	ㅤ
Content	Subject Line Finalized	Clear, non-spammy, on-brand	ㅤ	☐	ㅤ
ㅤ	Preview Text Finalized	Complements subject line, entices opens	ㅤ	☐	ㅤ
ㅤ	Body Content Proofed	No typos, consistent tone, brand voice	ㅤ	☐	ㅤ
ㅤ	CTA Buttons/Links Added	All call-to-action buttons work	ㅤ	☐	ㅤ
ㅤ	Personalization Tokens Validated	First name, company name, etc. inserted correctly	ㅤ	☐	ㅤ
Design	Responsive Design Tested	Mobile and desktop rendering confirmed	ㅤ	☐	ㅤ
ㅤ	Images Properly Sized & Hosted	ALT text included, no broken links	ㅤ	☐	ㅤ
ㅤ	Plain Text Version Reviewed	Not auto-generated gibberish	ㅤ	☐	ㅤ
ㅤ	Accessibility Considered	Contrast, font size, screen-reader compatibility	ㅤ	☐	ㅤ
Testing	Inbox Rendering Previewed	Litmus, Email on Acid, or ESP previews	ㅤ	☐	ㅤ
ㅤ	Spam Score Checked	Passed through Mail Tester or similar	ㅤ	☐	ㅤ
ㅤ	All Links Tested	UTM tags applied and working	ㅤ	☐	ㅤ
ㅤ	Send to Seed List	Internal QA before full deployment	ㅤ	☐	ㅤ
Technical	Sender Name & Email Correct	Matches brand + complies with SPF/DKIM/DMARC	ㅤ	☐	ㅤ
ㅤ	From Address Verified	Registered with ESP, SPF aligned	ㅤ	☐	ㅤ
ㅤ	Unsubscribe Link Working	Clearly visible and functional	ㅤ	☐	ㅤ
ㅤ	Footer Info Compliant	Includes company address, privacy policy, etc.	ㅤ	☐	ㅤ
Deployment	Send Date/Time Finalized	Consider time zone, send caps, and frequency	ㅤ	☐	ㅤ
ㅤ	Final Approval Received	All stakeholders signed off	ㅤ	☐	ㅤ
ㅤ	Campaign Scheduled/Sent	Confirm send happened successfully	ㅤ	☐	ㅤ
ㅤ	Post-Send Monitoring	Check for bounces, complaints, and early performance	ㅤ	☐	ㅤ

📄 Helpful Additional Cheat Sheets

List of all freemium email domains: https://gist.github.com/Artistan/9662757

List of email malformations I typically filter for:

Issue Type	Examples	How to Filter/Flag
Missing "@" symbol	`john.doe.com`, `johndoeemail.com`	`NOT CONTAINS "@"`
Missing "." after "@"	`john@doecom`, `hello@domain`	`NOT CONTAINS "." AFTER "@"`
Starts or ends with special characters	`.john@doe.com`, `john@doe.com.`	`STARTSWITH(".") OR ENDSWITH(".")`
Consecutive dots	`john..doe@example.com`	`CONTAINS ".."`
Too short	`a@b.c`	Length check: `LENGTH < 6`
No domain portion	`john@` or `john@.`	`NOT CONTAINS "."` after `@`
No local part (before @)	`@example.com`	`STARTSWITH("@")`
Nonsense strings or keyboard mashing	`asdfasdf@asdf.com`, `qwe@qwe.qwe`	Regex match for repeated characters or gibberish
Temporary/throwaway domains	`test@mailinator.com`, `abc@tempmail.com`	Filter by known temp domains (see below)
Obvious fake terms	`test@domain.com`, `fake@email.com`	`CONTAINS "test" OR "fake"`
Non-alphanumeric characters in domain	`john@doe!.com`	Regex for special characters in domain
Spaces in email	`john doe@example.com`	`CONTAINS " "`
Emails ending in numbers suspiciously	`test123456789@domain.com`	Regex for numeric endings
Multiple "@" symbols	`john@@example.com`	Count "@" > 1
HTML tags or JS	`<script>@email.com`	`CONTAINS "<" OR ">" OR "script"`
Test emails	test@test.com	Starts with `test@` (or you can experiment with contains, just be aware that some legitimate names look this way on corporate email, like Tim Estes could be testes@company.com)

Typical throwaway email domains:

mailinator.com

tempmail.com

10minutemail.com

guerrillamail.com

trashmail.com

yopmail.com

fakeinbox.com

List of more temp domains (source)

✍️ Enterprise Pro Tips

If you can get some budget, get a tool like Knak — seriously. Full transparency, I am an ambassador, but that’s because I really love their tool and used it in the Enterprise world — it saves you SO MUCH TIME in Enterprise campaign ops, especially if you have a centralized email/LP creation and deployment group but not the appropriate staffing to support your stakeholders.

If you are a public company, getting all of these email pieces right is even more important…there are lawyers and competitors just waiting for you to have a security issue or to send something legally ambiguous. Make sure you are keeping up with the latest compliance laws and your configurations are all set up correctly.

Beware of drastically changing your send volume overnight — if you go from emailing 10,000 people per day to 100,000+ people per day overnight, you could quickly be put on a blacklist….ESPECIALLY if you are emailing a stale database (think: M&A). It doesn’t matter that you have a larger database, it’s all about send size and data quality.

P.S. One thing I didn’t include in here is email consent compliance — this varies depending upon where your business is and where your prospects are. LMK if you want another guide about that, but it felt like too much to include in here. 😅

🗣️ Have feedback? This is a public resource for us all to use — please email me at sara@saramcnamara.com if you have any feedback or ways I can improve upon this!

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