One Unified Inbox for Lemlist. Every email and LinkedIn reply answered in under 5 minutes.
Lemlist runs multichannel sequences across email and LinkedIn. Underfive takes it from there. Replies from every channel, campaign and client land in one Unified Inbox, where AI inbox agents write a human-like response, send it back through Lemlist on the channel it came from, follow up, and book the meeting on your calendar.
- 50 free replies
- No credit card
- Email and LinkedIn in one inbox
Reply via Lemlist 
Read & classified
Interested · drafted in 48s 
Lemlist starts the conversation on every channel. Your Unified Inbox finishes it.
A multichannel sequence means replies arrive in more than one place: a reply to step 2 by email, a reply to step 4 on LinkedIn. The expensive gap is finding each one and answering it before the lead goes cold. Underfive puts every Lemlist reply in one inbox and answers it in minutes, on the right channel.
Reply time, on every channel
Email replies and LinkedIn replies from Lemlist sequences both get a human-like response in under five minutes, 24/7.
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.
Channels, one thread view
See the email and LinkedIn side of a Lemlist conversation together, so the agent answers with the full context of the sequence.
Connected in three steps
One API key. Email and LinkedIn replies flow in automatically.
Connect Lemlist with your API key
Copy your API key from Lemlist settings and paste it into Underfive under Integrations. Underfive registers the reply webhook with Lemlist for you, so replies from both the email and LinkedIn steps of your sequences start flowing into the Unified Inbox.
- One API key per Lemlist team
- Reply webhook created for you, no URLs to copy
- Email and LinkedIn steps both covered
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, on every channel.
- Knowledge base and reply logic per workspace
- Auto-send or Require Approval, per category
- Calendar connected for direct booking
Replies are answered on the channel they came from
When a prospect replies by email, the agent answers by email from the same mailbox. When they reply on LinkedIn, it answers on LinkedIn from the same profile. Interested prospects get a meeting on your calendar, whichever channel they used.
- Sent back through Lemlist, from the original sender
- Smart follow-ups when a thread goes quiet
- Every channel and client in one Unified Inbox
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 running Lemlist sequences? You are a few minutes away.
Sign up, paste your Lemlist API key, and the next reply to any step of any campaign gets handled. Nothing changes in your sequences, senders, or schedules.
What happens to each kind of reply
Your inbox agents classify every email and LinkedIn 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.
Multichannel outbound. One inbox for every reply.
Lemlist made multichannel outbound easy to run. Underfive makes it easy to answer. Each client or team gets its own agents, knowledge base, calendar and Slack channel, and every email and LinkedIn reply shows up in one view.
A workspace per client
Connect each client's Lemlist to its own Underfive workspace. Agents, knowledge and approvals stay separate per client.
Workspace Agent
Turn it on for a workspace and the agent handles every positive reply in that workspace without trigger keywords.
Trigger keywords for shared workspaces
Running several offers through one Lemlist team? Route replies to the right agent by keyword, such as a brand name or domain in the thread.
A workspace per client
Team members are unlimited on every plan and workspaces are unlimited on Agency, so adding a client never adds a per-seat fee on the reply side.
Two tools. One job each.
Lemlist owns multichannel sequencing and sending. The Underfive Unified Inbox owns everything after the reply lands.
| Capability | Lemlist | Underfive |
|---|---|---|
| Multichannel sequences across email and LinkedIn | — | |
| Personalization, sending and deliverability tools | — | |
| Replies collected inside your Lemlist team | ||
| One Unified Inbox across every tool, channel and client | — | |
| Writes a human-like reply to each response | — | |
| Replies within 5 minutes, 24/7, on email and LinkedIn | — | |
| Negotiates times and books the meeting | — | |
| Follows up when a thread goes quiet | — | |
| Approval queue with Slack notifications | — |
Lemlist integration FAQ
Everything people ask before connecting.
Does Underfive handle both email and LinkedIn replies from Lemlist?
Yes. Replies to the email steps and the LinkedIn steps of your Lemlist sequences both land in the Unified Inbox. The agent answers each one on the channel it came from, from the same mailbox or LinkedIn profile.
Do I have to set up a webhook in Lemlist manually?
No. When you paste your Lemlist API key into Underfive, Underfive registers the reply webhook with Lemlist for you. There are no URLs to copy.
Where do I find my Lemlist API key?
In Lemlist, open your settings and look for the API section. Each Lemlist team has its own key, so connect each team to Underfive separately if you run multiple clients.
Will this change my Lemlist campaigns?
No. Sequences, steps, schedules and senders keep running exactly as they do today. Underfive only acts on replies.
What does Underfive add on top of Lemlist?
Lemlist runs and sends the sequence. Underfive brings every reply from Lemlist and your other tools 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 clients on Lemlist. How does that work?
Create one Underfive workspace per client and connect each with its own Lemlist API key. Turn on the Workspace Agent so it handles every positive reply in that workspace. Team members are unlimited on every plan, workspaces are unlimited on Agency, and the Unified Inbox shows every client in one place.
What does it cost?
Start with 50 free replies and no credit card. After that, plans include the full platform plus a monthly allowance of agent credits. See the pricing page for current plans.
Stop leaving Lemlist replies unanswered.
Connect in under five minutes. Your first 50 replies are free, and nothing changes in your sequences.
Not on Lemlist yet? Learn about Lemlist.