GreatHorn is owned by Proofpoint, which acquired it in August 2022.

Where is GreatHorn headquartered?

GreatHorn is headquartered in Waltham, United States.

Who is the CEO of GreatHorn?

Kevin O'Brien is the CEO of GreatHorn.

Who founded GreatHorn?

Kevin O'Brien and Raymond Canzanese are co-founders of GreatHorn, founded in 2015.

Who are GreatHorn's competitors?

CyberSentriq, ExchangeDefender, and Gatefy are among the closest in Email & Messaging Security. The full competitive set, with overlap scoring, is in the platform.

What products does GreatHorn sell?

GreatHorn sells GreatHorn Email Security and GreatHorn Mailbox Intelligence.

GreatHorn

Email & Messaging SecurityWaltham, United Statesfounded 2015acquired by Proofpointgreathorn.com ↗

GreatHorn is a cybersecurity company specializing in Email & Messaging Security, founded in 2015 and headquartered in Waltham, United States. It has raised $21.93M in equity across 5 priced rounds, employs about 7 people, and was acquired by Proofpoint in 2022.

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updated Oct 18, 2026

Latest GreatHorn news and company activity

What GreatHorn did, dated — selected moves from the record, one per kind, newest first.

Sep 2022AcquiredProofpoint Signs Definitive Agreement to Acquire GreatHorn
Jun 2017Funding roundGreatHorn Secures $6.3 Million Series A Funding
Mar 2016Funding roundGreatHorn Raises $2.25M Seed Funding
Dec 2015PartnershipGreatHorn Announces Partnership With Microsoft

GreatHorn products

GreatHorn funding

GreatHorn has raised $21.93M in priced equity. Its most recent round was a Venture Round in February 2022. It has 5 funding rounds on record: Pre-Seed, Seed, Series A, Series B, and Venture Round. 9 investors are on record, including Techstars and .406 Ventures.

Equity raised: $21.93M5 priced rounds
Last round: Venture RoundFeb 2022

View the complete funding history

GreatHorn employees and hiring

As of September 2026, GreatHorn has about 7 employees.

Employees: 7
Open roles: 0

See hiring trends

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The other 440 data points.

Funding historyevery round, every investor named
Headcount growthvelocity, departments, seniority
Open jobslive postings, hiring pace, role mix
Tech stackframeworks, clouds, security
Competitorsfull set, overlap scored
Leadershipevery exec, with roles
Customersnamed publicly, with sources
Reviews & newssentiment, coverage, cadence

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Funding, round by round, with the investors
Headcount, hiring and the people
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The other 440 data points.

Funding historyevery round, every investor named
Headcount growthvelocity, departments, seniority
Open jobslive postings, hiring pace, role mix
Tech stackframeworks, clouds, security

Similar in Email & Messaging Security

Common questions about GreatHorn.

How much funding has GreatHorn raised?: GreatHorn has raised $21.93M in priced equity. Its most recent round was a Venture Round in February 2022. It has 5 funding rounds on record: Pre-Seed, Seed, Series A, Series B, and Venture Round. 9 investors are on record, including Techstars and .406 Ventures.
How many people work at GreatHorn?: As of September 2026, GreatHorn has about 7 employees.
Who owns GreatHorn?: GreatHorn is owned by Proofpoint, which acquired it in August 2022.
Where is GreatHorn headquartered?: GreatHorn is headquartered in Waltham, United States.
Who is the CEO of GreatHorn?: Kevin O'Brien is the CEO of GreatHorn.
Who founded GreatHorn?: Kevin O'Brien and Raymond Canzanese are co-founders of GreatHorn, founded in 2015.
Who are GreatHorn's competitors?: CyberSentriq, ExchangeDefender, and Gatefy are among the closest in Email & Messaging Security. The full competitive set, with overlap scoring, is in the platform.
What does GreatHorn do?: GreatHorn is a cybersecurity company specializing in Email & Messaging Security, founded in 2015 and headquartered in Waltham, United States.