One Unified Inbox for Gmail. Every reply answered in under 5 minutes.
Gmail and Google Workspace already run your mail on your own domain. Underfive connects straight to it with Google OAuth, no third-party sequencer in between. Every reply to your outreach lands in one Unified Inbox, where AI inbox agents write a human-like response, send it from the same mailbox, follow up, and book the meeting on your calendar.
- 50 free replies
- No credit card
- Sign in with Google, no webhook
Reply via Gmail 
Read & classified
Interested · drafted in 48s 
Gmail gets the reply. Your Unified Inbox wins the meeting.
Replies already arrive in your Gmail inbox. The expensive gap is the hours between a prospect replying and someone on your team finding it, reading it, and writing back. Underfive closes that gap with one inbox across every mailbox and agents that answer in minutes.
Reply time, around the clock
Every reply to your outreach gets a human-like response in under five minutes. Nights, weekends, and holidays included.
More likely to qualify the lead
Harvard Business Review found that firms contacting a lead within an hour were nearly seven times more likely to qualify it, meaning they reached a real decision maker, than firms that waited an hour longer (Oldroyd, McElheran and Elkington, HBR, March 2011). That window is the whole product.
Webhooks. Sign in with Google.
Connect each Gmail or Google Workspace mailbox with Google's OAuth flow. No sequencer, no webhook URL, no forwarding rules. Your Google password is never stored by Underfive.
Connected in three steps
Sign in with Google, add your warm-up phrases, and you are connected. No sequencer required.
Connect Gmail with Google OAuth
In Underfive, choose Gmail under Integrations and sign in with the Google account you send from. Google's OAuth flow grants Underfive read and send access to that mailbox, and your password stays with Google. An admin adds the Google Client ID once under Inbox in the admin panel, and every mailbox under that workspace can then connect the same way.
- Google OAuth, no third-party sequencer and no webhook
- One-time Client ID setup per admin workspace, then each mailbox signs in
- Add your warm-up phrases so warm-up traffic never reaches the Unified Inbox
Integrations · Add tool Teach your inbox agents how you sell
Upload your offer, FAQs, pricing, and objection handling. Connect Google Calendar or Outlook. Then decide which reply categories send automatically and which wait for a human.
- Knowledge base and reply logic per workspace
- Auto-send or Require Approval, per category
- Calendar connected for direct booking
Replies are answered, followed up, and booked
When a prospect replies, the thread appears in your Unified Inbox. An inbox agent reads it, classifies it, writes a response in your voice, and sends it from the same Gmail mailbox. Interested prospects get a meeting on your calendar.
- Sent from the mailbox that received the reply, so the prospect sees one continuous thread
- Smart follow-ups when a thread goes quiet
- Every conversation in one Unified Inbox across mailboxes and clients
Unified Inbox- Meeting bookedJordan MeyerThursday at 10:30 works. Talk then.Meeting booked
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Replied · autoEmily TranCan you send over a case study first?Replied · auto -
Follow-up · Apr 2Omar HaddadWe're mid-contract until Q2, circle back then?Follow-up · Apr 2 -
Needs approvalLena SchulzWho else at your company should I loop in?Needs approval
Already sending from Google Workspace? You are five minutes away.
Sign up, sign in with Google, add your warm-up phrases, and the first reply that lands in your Gmail mailbox gets handled. Nothing changes in how you send.
What happens to each kind of reply
Your inbox agents classify every email reply before they act. You decide which categories auto-send and which wait for a human.
Interested
Answers, proposes times, and books the meeting on your calendar.
Pricing question
Replies with the pricing guidance from your knowledge base and moves toward a call.
Product question
Answers from your FAQs and offer details, in your tone of voice.
Objection
Handles the objection using your playbook and keeps the thread alive.
Not right now
Acknowledges, then schedules a follow-up for the timeframe they gave.
Referral
Thanks them and continues the conversation with the person they named.
Not interested
Closes politely and stops the thread. No more follow-ups.
Uncategorized
Goes to the approval queue so a human decides. Nothing is sent blind.
Categories and their behaviour are yours to edit per workspace. Nothing is sent without a category you approved.
Your own mailboxes. One inbox for all of them.
Founders and small teams often send from their own Google Workspace mailboxes without a sequencer in front of them. Underfive connects each mailbox directly, so every reply across every mailbox and every workspace shows up in one view, with agents, knowledge, and approvals kept separate where you want them.
One Client ID, many mailboxes
An admin adds the Google Client ID once under Inbox in the admin panel. After that, every mailbox under the workspace connects with a Google sign-in.
Warm-up and ignore phrases
Add the subject lines or tags your warm-up tool uses, or connect your sequencer and Underfive pulls them in. Matching threads are removed from the Unified Inbox so agents only handle real replies. Add extra ignore phrases for anything else you want kept out.
One workspace per client or brand
Running several brands or clients from separate Google Workspace domains? Give each its own Underfive workspace with its own agents, knowledge base, calendar, and Slack channel.
A workspace per client
Team members are unlimited on every plan and workspaces are unlimited on Agency, so adding a mailbox or a teammate never adds a per-seat fee on the reply side.
Two tools. One job each.
Gmail owns sending and receiving on your domain. The Underfive Unified Inbox owns everything after the reply lands.
| Capability | Gmail | Underfive |
|---|---|---|
| Send and receive mail on your own domain | — | |
| Labels, filters, search, and storage | — | |
| Replies land in the mailbox that sent the email | ||
| One Unified Inbox across every mailbox and client | — | |
| Writes a human-like reply to each response | — | |
| Replies within 5 minutes, 24/7 | — | |
| Negotiates times and books the meeting | — | |
| Follows up when a thread goes quiet | — | |
| Approval queue with Slack notifications | — |
Gmail integration FAQ
Everything people ask before connecting.
How does the Gmail connection work? Is there a webhook?
No webhook. You sign in with Google and the OAuth flow grants Underfive read and send access to that mailbox. Underfive then watches the mailbox for replies and sends responses from it. There is no sequencer or forwarding rule in between.
What is the Client ID and where does it go?
The Client ID is a one-time setup an admin does in the Underfive admin panel under Inbox. Once it is in place for your admin workspace, every Gmail or Google Workspace mailbox under that workspace can connect with a Google sign-in. You do not repeat it per mailbox.
Does Underfive reply from my Gmail mailbox?
Yes. Replies are sent from the same Gmail mailbox that received the reply, so the prospect sees one continuous thread from the same person.
Will this change how I send?
No. Keep sending from Gmail, Google Workspace, or whatever sits in front of them exactly as you do today. Underfive only acts on replies.
What are warm-up phrases, and what about my personal mail?
Warm-up tools send automated emails through your mailbox. Add the subject lines or tags they use as warm-up phrases, or connect your sequencer and Underfive pulls them in. Threads that match are removed from the Unified Inbox so your inbox agents only process real replies and no reply credits are spent on warm-up traffic. You can add extra ignore phrases to keep any other mail out of the Unified Inbox.
Gmail already has an inbox. What does Underfive add?
Gmail shows one mailbox at a time. Underfive brings replies from every Gmail mailbox, every workspace, and every other tool into one Unified Inbox, and its inbox agents actually write and send the response, follow up, and book the meeting.
Can I review replies before they go out?
Yes. Each reply category can be set to auto-send or require approval. Replies that need approval wait in your Underfive queue, and you can approve them from the app, from Slack, or through the Underfive MCP connector.
I run several brands or clients on Google Workspace. How does that work?
Create one Underfive workspace per brand or client and connect its Gmail mailboxes with Google sign-in. Agents, knowledge, approvals, and Slack channels stay separate per workspace. Team members are unlimited on every plan, workspaces are unlimited on Agency, and the Unified Inbox shows everything in one place. Running hundreds or thousands of mailboxes from a provider like Zapmail, Inboxy, or MissionInbox? Do not connect them one by one. Book an onboarding call and our team connects them in bulk. Underfive is already integrated with Zapmail.
What does it cost?
Start with 50 free replies and no credit card. After that, plans are priced by agent credits. See the pricing page for current plans.
Stop leaving Gmail replies unanswered.
Sign in with Google and connect in under five minutes. Your first 50 replies are free, and nothing changes in how you send.
Not on Google Workspace yet? Learn about Google Workspace.