A Private Custom Domain EmailFor Startups & Scaleups
Own your email communication without the per-seat overhead — get custom domain mailboxes that scale effortlessly with your team.
Dedicated Domain Identity
(not shared or rate-limited public pools)
60-second setup first
instant DNS records & clarity before heavy lifting
Privacy-first architecture
clean mailboxes & systems you actually own
Managing email infrastructure wasn't supposed to be your second job.
Between shipping features, closing clients, and scaling operations, email deliverability fires keep pulling you away from growth. If any of this sounds familiar, you're not alone:
DNS & Deliverability Drain
SPF, DKIM, and MX records fail silently and critical business emails land in spam.
Per-Seat Pricing Bloat
Paying $10-$30/user every month just for shared inbox aliases, bots, and support handles.
Privacy You Keep Compromising
Big tech scanning inbox contents and mining domain communication for ad targeting.
Start where you are — then we'll guide you to the right setup
I'm dealing with email chaos
Deliverability is failing, DNS setup is confusing, and per-seat fees keep escalating.
I want to see how Kosh works
Explore how Kosh handles custom domain routing, automated DKIM/SPF, spam defense, and inbox UI.
Connect Domain
Verify DNS & ownership in 60 seconds
Auto-DKIM & SPF
Cryptographic keys and deliverability records
Send & Receive
Modern webmail, spam filters & REST APIs
I'm ready to upgrade right now
Claim your custom domain mailboxes and write from you@yourdomain.com in 60 seconds.
you@startup.com
● DKIM Verified
What we help you build with your custom email stack
Kosh plugs in as your complete domain email engine — building rock-solid deliverability, securing privacy, and giving your team mailboxes that just work.
Custom Domain Foundations
Automated DNS records, 1-click MX verification, multi-domain management, and custom aliases from day one.
High-Deliverability Inboxes
Built-in SPF, DKIM, and DMARC alignment that ensures your emails land straight into the primary inbox, never spam.
Spam Defense & Hashcash
Cryptographic proof-of-work spam defense and heuristic filters that protect your domains from junk and phishing.
Developer REST APIs & Webhooks
Programmatically send, receive, parse, and route domain emails with instant webhooks and modern SDKs.
Session & Device Security
Active device tracking, remote session revocation, encrypted mailbox storage, and detailed security logs.
Modern Webmail Experience
Sub-second search, responsive keyboard navigation, dark mode, rich message compose, and zero ad telemetry.
Supporting teams & founders across the globe
Kosh delivers lightning-fast email infrastructure worldwide — zero per-seat lock-in, with instant DNS verification and rock-solid deliverability that scales with your growth.
Questions?
We're here to help
Get custom domain email, team inboxes, and seamless integration. No fragmentation, no vendor lock-in.