Gmail outreach that knows your contacts
CMass uses Claude AI to write a unique, personalized opening line for every recipient — based on the data you import from Google Sheets or CSV. No Claude account needed. AI is built into every plan.
No credit card required · Works with Gmail & Google Workspace
Recipients
Email Preview — sarah@acme.com
Subject: Quick question about {company}
Hi Sarah,
✦ ClaudeSaw Acme just expanded to EMEA — exciting timing for what I want to share.
Would love 15 minutes to show you how CMass can help your team scale outbound without leaving Gmail...
The AI that actually understands your relationships
Most "AI personalization" is just a spinner — it mixes your merge tags into a template. CMass uses Claude to genuinely reason about each contact and write something real.
Today Claude reads the data you import — every column in your Google Sheet or CSV. We're building toward a world where Claude also knows about every meeting you've had, every deck you've shared, who attended, and what was discussed — so your outreach always sounds like it was written by someone who actually knows the person.
No Claude account needed
CMass has its own Anthropic API integration. Claude is built into every plan — you don't need to sign up for Claude.ai or manage any API keys.
What Claude reads to write your email
Sheet & CSV data
LiveEvery column from your import — name, company, role, custom fields
Merge tag values
LiveAny field you include becomes Claude context
Email thread history
Coming soonPrevious conversations with each contact
Meeting history
Coming soonDates, duration, and agenda
Shared decks & docs
Coming soonProposals, one-pagers, pitches
Meeting attendees
Coming soonWho was invited and who showed up
The vision
Outreach that knows the whole story
Imagine emailing someone you met last week. Before you type a word, CMass already knows the meeting date, who attended, what was discussed, and the proposal deck you shared. Claude reads all of it and writes the follow-up.
What CMass will know before you send
Met with Sarah Chen on May 14th — 42 min call, 3 attendees
Sarah and Tom from Acme attended. Their VP was invited but didn't show
You shared the Q2 Outbound Playbook deck during the meeting
Sarah replied to your intro email 3 days before the call
Follow-up was promised within 5 business days — you're on day 4
✦ Claude writes
"Hi Sarah, great speaking with you and Tom last week — hope the VP got caught up on our conversation. Following up on the playbook I shared, particularly the section on automated sequences that we talked about..."
100% Built with Claude. This is where CMass is headed — start using what's live today.
Add to Chrome — FreeEverything else you need
The Gmail mail merge foundation that serious senders rely on — built to grow with Claude's capabilities.
Google Sheets Mail Merge
Import contacts from any Google Sheet. Every column becomes a merge tag — {Company}, {Role}, {Custom} — no setup required.
Unlimited Follow-up Stages
Set as many follow-up stages as you want. Send only to non-openers, non-repliers, or everyone — per stage, on your schedule.
Real-time Analytics
Per-recipient open and click tracking. Know exactly who engaged, when, and how many times — without leaving Gmail.
Bounce Suppression
Bad addresses are automatically blocked from all future campaigns. Your sender reputation stays clean without you lifting a finger.
Stays in Gmail
Every email lives in your Sent folder. Replies land in your inbox. No separate portal, no third-party dashboard to babysit.
Instant Setup
Install the Chrome extension, connect your Google account, and send your first campaign in under 5 minutes.
Up and running in 5 minutes
No complicated setup. No new inbox. Just Gmail — with Claude inside.
Install CMass
Add the Chrome extension — it embeds directly into Gmail. No new app, no new inbox.
Import your list
Paste emails, upload a CSV, or link a Google Sheet. Columns map to merge tags automatically.
Let Claude write
Turn on AI personalization and Claude reads every column in your data to write a unique line per recipient.
Send & track
Hit send. Watch opens and clicks come in on your real-time dashboard.
Loved by senders
"The Claude personalization is what got me. Every email reads like I wrote it myself. Reply rates doubled in the first week."
Sarah K.
Head of Growth, Fintech startup
"I linked a Google Sheet, every column became a merge tag, Claude wrote the opening line — done. Took 8 minutes."
Marcus T.
Founder, B2B SaaS
"I was on GMass for two years. Switched for the unlimited follow-up stages alone. The AI is a bonus."
Priya N.
Sales Lead, Agency
✦ Powered by Claude
Start sending smarter today
Free plan includes 50 emails/day, Google Sheets import, Claude AI personalization, and analytics. No credit card needed.
Frequently asked questions
Does CMass work with my existing Gmail account?↓
Yes. CMass connects to your Gmail via the official Google API. You keep your domain, your inbox, and your sender reputation.
How is CMass different from GMass?↓
CMass is built around Claude AI. Instead of basic merge tags, Claude reads your data and writes a genuinely personalized sentence per recipient. We also offer unlimited follow-up stages, per-stage send conditions, and automatic bounce suppression.
Do I need a Claude or Anthropic account?↓
No. CMass has its own Anthropic API integration — Claude is built into every plan, free and paid. You don't need a Claude.ai subscription, an Anthropic account, or any API keys. We handle all of that so you don't have to.
What does "powered by Claude" actually mean?↓
Claude is Anthropic's AI model — the same one behind Claude.ai. When you turn on AI personalization in CMass, Claude reads each recipient's data from your sheet (name, company, role, and any custom columns) and writes a unique opening line for that person. It's not a template spinner — it reasons about each contact individually.
Is there a free plan?↓
Yes. The free plan includes 50 emails per day, Google Sheets import, merge tags, and basic analytics. No credit card required.
Is CMass CAN-SPAM and GDPR compliant?↓
Yes. Every campaign includes a one-click unsubscribe link. CMass automatically suppresses unsubscribes and bounces from all future sends.
What's coming with meetings and decks?↓
We're building Google Calendar and Drive integrations so Claude can read your meeting history, shared proposals, and attendee context before writing your outreach. Sign up for early access on the features page.