Shutdown
Current service notice says Inboxbooster has shut down and directs users to email for recommendations on other tools.
SourceCompany research
Public company, workplace, funding, and market signals
Updated Jul 30, 2026
Overview
Inboxbooster was a YC W17, San Francisco email deliverability startup that tested inbox placement, DNS/authentication, domain reputation, and content triggers, with consulting plans for harder cases; public pages now indicate the service has shut down and the domain is for sale.
Primary product
Email deliverability monitoring and inbox-placement testing platform
Founded
2016
Headquarters
San Francisco, California, United States
Team size
2-10 employees
Industry
IT Services and IT Consulting
Sub-industry
Email deliverability software
Business model
freemium
subscription
consulting services
Funding
Stage
pre-seed
Total raised
$1M
Latest round
Pre-Seed · Apr 2023
Latest amount
$1M
Apr 2023
People & investors
Leadership
Founder and CEO
Founders
Co-founder
Work & culture
Founder-led and very small; public launch copy emphasizes direct customer feedback, fast iteration, and a hands-on two-person founding team.
Product & market
Pricing
Free inbox-placement tests plus paid monthly consulting plans (basic around $300/month and premium around $1,500/month).
Differentiators
- —Free comprehensive inbox-placement test
- —Explains why messages land in spam or promotions
- —Checks DNS, domain reputation, and content triggers
- —Consulting plans for difficult deliverability issues
- —Open-source/technical tooling around email infrastructure
Technology
Google Cloud Platform
Cloud Functions
Cloud Pub/Sub
ESP webhooks
SMTP/MTA
DNS
SPF
DKIM
DMARC
header analysis
content analysis
reputation checks
Customers
Y Combinator
Zengo
Wizbii
small businesses
individual senders
Competitors
Everest
Pendula
Sender.net
Radica Systems
MailMonitor
Scale & contact
Estimated revenue
Around $330K ARR (2025 estimate)
Estimated monthly visits
106
Traffic estimate as of Jul 2026
Signals & risks
Other
InboxBooster.com is listed for sale on Atom, indicating the original domain is being brokered rather than actively operated.
SourceLatest news
FinSMEs · Apr 2023
Reported the $1M pre-seed round, citing Y Combinator and angel investors.
BusinessMole · Apr 2023
Described the launch story, the funding round, and early traction around fixing Y Combinator email deliverability.
Y Combinator · Apr 2023
YC launch post explaining the product and the founders' approach to inbox placement and deliverability.
Inboxbooster
Current app notice says Inboxbooster has shut down and invites users to email for recommendations on other tools.
Jobs and careers at Inboxbooster
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