What is a Unified Inbox?
A unified inbox brings every reply from every sending tool, channel, and client into one view. A unified inbox with AI goes further: inbox agents read each reply, answer it in under 5 minutes, follow up, and book the meeting.
Underfive is a Unified Inbox with AI, built for sales and outbound teams.
- 50 free replies
- No credit card
- Setup in under 5 minutes
Smartlead 
Instantly 
Email Bison 
HeyReach 
Gmail 
Outlook 
LinkedIn 
Unified Inbox-
Meeting bookedJordan Meyer via Email BisonThursday at 10:30 works. Talk then.Meeting booked -
Replied · autoEmily Tran via SmartleadCan you send over a case study first?Replied · auto -
Follow-up · Apr 2Omar Haddad via HeyReachWe're mid-contract until Q2, circle back then?Follow-up · Apr 2 -
Needs approvalLena Schulz via InstantlyWho else at your company should I loop in?Needs approval
Google CalendarOutlook
Slack
GoHighLevel
HubSpot What a Unified Inbox with AI actually does
Collecting replies is table stakes. The value is in what happens to each one in the first five minutes.
One place for every reply
Cold email replies, LinkedIn DMs, and inbound from every sending tool and every client workspace land in a single view. No more tabbing between sequencers to find out who answered.
Agents that reply, not just sort
AI inbox agents read each thread, classify the intent, and send a human-like reply from the same sender in under 5 minutes. They answer questions, handle objections, and follow up when a thread goes quiet.
Meetings booked, not just promised
When a prospect is interested, the agent proposes times from your real calendar, negotiates, and sends the invite. The thread is marked Meeting Scheduled and your team is notified.
Humans where you want them
Every reply category is either auto-send or require approval. Approvals wait in a queue you can clear from the app, from Slack, or through the MCP connector. Nothing goes out blind.
Unified Inbox vs everything that looks like one
Several tools show you replies. Only one answers them.
- Replies from every sending tool in one viewNoNoPartlyYes
- Every client and workspace in one viewPartlyNoPartlyYes
- Email and LinkedIn replies togetherNoPartlyPartlyYes
- Writes and sends the reply for youNoNoNoYes
- Replies in under 5 minutes, 24/7NoNoNoYes
- Sends from the original sender and toolNoYesPartlyYes
- Proposes times and books the meetingNoNoPartlyYes
- Follows up when a thread goes quietNoPartlyPartlyYes
- Human approval, from the app or SlackPartlyNoNoYes
- Keeps your CRM pipeline in syncNoNoYesYes
| What you need | Shared team inbox Front, Help Scout, Missive | Your sequencer's inbox Smartlead, Instantly | CRM HubSpot, GoHighLevel | Underfive Unified Inbox with AI |
|---|---|---|---|---|
| Replies from every sending tool in one view A sequencer shows its own campaigns. A CRM shows what gets logged to it. | No | No | Partly | Yes |
| Every client and workspace in one view | Partly | No | Partly | Yes |
| Email and LinkedIn replies together | No | Partly | Partly | Yes |
| Writes and sends the reply for you | No | No | No | Yes |
| Replies in under 5 minutes, 24/7 | No | No | No | Yes |
| Sends from the original sender and tool | No | Yes | Partly | Yes |
| Proposes times and books the meeting | No | No | Partly | Yes |
| Follows up when a thread goes quiet | No | Partly | Partly | Yes |
| Human approval, from the app or Slack | Partly | No | No | Yes |
| Keeps your CRM pipeline in sync | No | No | Yes | Yes |
| Best at | Assigning one mailbox to a team | Seeing replies inside one tool | Keeping the system of record | Answering every reply, fast |
Keep the tools you have. Underfive sits on top of your sequencers and CRM and handles the part none of them do: the reply.
See how inbox agents replyWho runs on a Unified Inbox
Agencies
One workspace per client, one inbox across all of them. Each client gets its own inbox agents, knowledge base, calendar and Slack channel, with no per-seat fee.
Read moreSales teams
Reps stop living in sequencer inboxes. The Unified Inbox handles first responses and follow-ups so reps only step in for approvals and calls.
Read moreFounders
Run outbound at volume without hiring an SDR. Replies get answered at 2 AM, meetings land on your calendar, and you review what matters.
Read moreUnified Inbox FAQ
What is a unified inbox?
A unified inbox is a single view that collects messages from many sources, such as several email accounts, sending tools, or channels, so you can read and act on all of them in one place instead of switching between tools.
What is a unified inbox with AI?
A unified inbox with AI goes a step further than collecting messages. AI inbox agents inside the inbox read each reply, classify it, write a human-like response, send it from the original sender, follow up, and book meetings. Underfive is a unified inbox with AI built for sales and outbound teams.
How is a unified inbox different from a shared inbox?
A shared inbox gives several people access to one mailbox. A unified inbox brings many mailboxes, tools, and channels into one view. Underfive adds AI inbox agents on top, so the replies are answered as well as collected.
Which tools can feed the Underfive Unified Inbox?
Smartlead, Instantly, Email Bison, PlusVibe, Lemlist, HeyReach, Aimfox, Expandi, GetSales, Gmail, and Outlook. Replies are answered through the same tool and sender they arrived from, and meetings, alerts, and pipeline updates go out to Google Calendar, Outlook, Slack, GoHighLevel, and HubSpot.
Do the agents send replies without me seeing them?
Only for the reply categories you set to auto-send. Anything set to require approval, and anything the agent cannot classify, waits in the approval queue. You can approve from the app, from Slack, or through the MCP connector.
Does it replace my sending tool?
No. Your sequencer keeps doing sending, warm-up, and deliverability. The Unified Inbox takes over the moment a reply lands and hands the conversation back when a human needs to step in.
How fast do replies go out?
Under 5 minutes, 24 hours a day, including weekends. Harvard Business Review found that firms contacting a lead within an hour were nearly seven times more likely to qualify it than firms that waited an hour longer (HBR, March 2011).
What does it cost?
Start with 50 free replies and no credit card. After that, plans are priced by agent credits and include unlimited team members and inbox agents, with workspaces from 1 on Professional to unlimited on Agency.
One inbox. Every reply answered.
Connect your sending tools in under five minutes. Your first 50 replies are free.