Why does warmup (and auto-stop-on-reply) need incoming access?

Short answer: because warmup and auto-stop-on-reply both need to read your inbox, and reading the inbox needs incoming (IMAP) access — not just outgoing (SMTP). Outgoing lets a mailbox send. Incoming lets WarmySender see what arrived. Warmup only works if it can watch friendly warmup mail land in your inbox (or spam) and act on it, and campaign follow-ups only stop automatically when someone replies if they can see that reply come in. If a mailbox is connected outgoing-only, it can still send, but it can't do those receive-and-measure steps — so the fix is simply to add incoming (IMAP) access. With Gmail or Outlook, signing in sets up both at once.

WarmySender runs your outreach on autopilot with AI agents, across Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel sequences — plus real-time email verification. Incoming access is what powers the Email Warmup channel and the reply-aware side of the Cold Email channel.

Incoming vs. outgoing, in one line each

• Outgoing (SMTP) is how mail leaves your mailbox. It's the "send" half — it powers your campaign sends and the outgoing side of warmup.
• Incoming (IMAP) is how WarmySender reads what arrives in your mailbox. It's the "see" half — it's what lets warmup measure results and lets campaigns notice replies.

Both are standard settings you'll recognise from setting up email in any mail app. Most warmup and campaign features that feel "smart" — the measuring, the rescuing, the auto-stopping — live on the incoming side, because they all depend on seeing what landed in the inbox.

How warmup uses your inbox

Warmup isn't just a matter of sending mail out. The whole point is to build your sender reputation by having real, friendly conversations land in real inboxes — and to prove they're landing. That proof lives in the receiving mailbox. Here's the loop, and why each step needs incoming access:

• Your inbox receives warmup mail. Friendly warmup emails arrive in your mailbox from the warmup network. Seeing them arrive is only possible with incoming access.
• WarmySender measures where they landed. Did the warmup mail reach the inbox, or get filtered to spam? That inbox-versus-spam placement is the single most important signal in warmup — and reading it means reading the inbox.
• Anything caught in spam gets rescued. When warmup mail lands in spam, WarmySender moves it back to the inbox and marks it as wanted — exactly what a real person does with a good email that got misfiled. That rescue teaches inbox providers your mail is legitimate, and it can only happen from inside the receiving mailbox.
• The friendly replies happen too. Warmup conversations include replies, which build the natural back-and-forth pattern that earns trust — again, something that only works when the inbox can be read.

So with an outgoing-only connection, a mailbox can send warmup mail, but WarmySender can't see it arrive, can't tell inbox from spam, and can't rescue anything — which is most of what makes warmup work. Adding incoming access turns the full loop on. For the bigger picture of how warmup builds up over time, see how email warmup ramps up.

How auto-stop-on-reply uses your inbox

A cold email campaign should stop emailing someone the moment they reply — chasing a person who's already answered is the fastest way to annoy a prospect and hurt your reputation. WarmySender does this for you automatically, and the way it works is by watching your inbox for their reply.

When a prospect replies, that message arrives in your mailbox. With incoming access, WarmySender sees it and quietly stops the remaining follow-ups for that person, so they never get a "just checking in" after they've already written back. Without incoming access, there's nothing to watch — the mailbox can keep sending, but it can't notice the reply, so the polite auto-stop can't kick in. This is why we strongly recommend incoming access for any mailbox you send campaigns from.

Which mailbox the reply lands in — and why it matters

By default a reply comes back to the address the email was sent from. So if a campaign sent from [email protected], the prospect's reply arrives at [email protected] — and that is the mailbox that needs incoming access for the auto-stop to work.

A step can optionally name a different reply-to address, and then replies land there instead. Worth knowing before you use it: WarmySender still watches the sending mailbox for replies, so if answers are routed to an inbox you haven't connected here, the automatic stop-on-reply won't see them and follow-ups will keep going. If you point replies somewhere else, connect that inbox too — or leave the field empty and replies come back to the sending address, which is what most campaigns want.

This is worth checking when a campaign keeps sending follow-ups even though you're sure someone replied. The usual cause is that the reply is sitting somewhere WarmySender can't see:

• You're reading replies somewhere else. If the sending mailbox forwards a copy to a different address, or your team reads replies in a shared inbox or a CRM, you'll see the reply — but WarmySender is watching the sending mailbox, so the copy elsewhere doesn't reach it. Give the sending mailbox incoming access and the auto-stop works.
• The sending mailbox is connected send-only. It can send perfectly, but it can't see anything arrive — including replies. Adding incoming access is the whole fix.
• You send from several mailboxes. Each one receives its own replies, so each one needs incoming access. A campaign rotating across four mailboxes only auto-stops reliably when all four can be read.

If you send from an alias (the From address differs from the account you sign in with), the reply still comes back to the alias, and your provider delivers it to the inbox that owns the alias — so connecting that mailbox covers it. See Connect a Gmail or Google Workspace alias for the full field mapping.

What you get with send-only — and what you're missing

The takeaway: outgoing-only isn't broken, it's just half the picture. It can send, but it can't do the measuring, rescuing, and reply-aware parts that make warmup effective and campaigns polite. Adding incoming access unlocks the full experience — and it's a one-time setup.

How to add incoming (IMAP) access

• Gmail and Outlook: the easiest path is to connect by signing in. On a personal mailbox that single sign-in sets up both incoming and outgoing in one step, and you get the full warmup and auto-stop experience out of the box. One exception worth knowing: if the mailbox is managed by an organisation — a Microsoft 365 or Google Workspace account — sending and reading are two permissions your administrator grants separately, and they can allow sending while leaving reading switched off. The sign-in still succeeds and the mailbox still sends, so nothing looks wrong, but nothing can be measured either. If your warmup shows nothing arriving, read Why can't WarmySender read my inbox? — it has the exact steps for an administrator to switch reading on. And if you check and reading is already switched on, stop there and tell us: the administrator's setting is the most common reason we cannot open an inbox, but it is not the only one — the connection can also fail for reasons that have nothing to do with your account. Send us the mailbox address rather than changing anything else, and we will take it from there. That page covers this case too.
• Other providers (your own domain or hosting): when you add the mailbox, fill in the incoming (IMAP) details next to the outgoing (SMTP) ones. These are the same server address, username, and password you'd use to set the mailbox up in any mail app — your provider lists them in their email-setup help. For providers other than Gmail and Outlook you generally use your normal mailbox password (no special app password needed) — see connecting mailboxes without app passwords.

Once incoming access is in place, warmup starts measuring and rescuing, and your campaigns start auto-stopping on replies — no further action needed on your part.

A quick example

Suppose you connect a mailbox on your own domain with outgoing details only, turn on warmup, and launch a campaign. Everything sends — warmup mail goes out, campaign emails go out — so at a glance it looks fine. But your warmup results stay flat because WarmySender can't see whether the warmup mail is reaching inboxes or being filtered, and it can't rescue anything from spam. And if a prospect replies, your follow-ups keep going, because nothing is watching the inbox to notice the reply.

Now you go back and add the incoming (IMAP) details for that same mailbox. Immediately the picture changes: warmup begins reporting inbox-versus-spam placement and rescuing misfiled mail, your reputation starts building the way it should, and the next time a prospect replies their remaining follow-ups stop on their own. Same mailbox, same sending — the difference is that WarmySender can now see, which is what turns on the smart half of both features.

Frequently asked questions

Why can't warmup just work with send-only access?

Because warmup's whole job is to prove your mail reaches inboxes and to fix it when it doesn't — and both of those live in the receiving mailbox. Warmup needs to see the friendly warmup mail arrive, tell whether it landed in the inbox or spam, and move anything caught in spam back to the inbox. All of that means reading the inbox, which needs incoming (IMAP) access. A send-only (outgoing/SMTP) connection can send warmup mail, but it can't see it arrive or act on it, so the measuring and rescuing that make warmup effective simply can't run.

What's the difference between incoming (IMAP) and outgoing (SMTP)?

Outgoing (SMTP) is how mail leaves your mailbox — the "send" half. Incoming (IMAP) is how WarmySender reads what arrives in your mailbox — the "see" half. They're the same two settings you'd enter to set up email in any mail app. Sending features use the outgoing side; the smart features that measure warmup results and notice replies use the incoming side.

How does the campaign stop emailing someone once they reply?

By watching your inbox for their reply. When a prospect writes back, their message lands in your mailbox, and with incoming (IMAP) access WarmySender sees it and automatically stops the remaining follow-ups for that person — so they never get a "just checking in" after they've already answered. Without incoming access there's nothing to watch, so the auto-stop can't run and follow-ups could keep going. That's why we recommend incoming access on any mailbox you send campaigns from.

Which inbox do replies to my campaign go to?

To the address the email was sent from, unless that step names a different reply-to address (an optional field — leave it empty and replies come back to the sender). That also means the sending mailbox is the one that needs incoming (IMAP) access for follow-ups to stop automatically: if you read replies in a forwarded copy, a shared inbox, or your CRM, WarmySender is still watching the mailbox that sent the email, so it won't see the reply there. If you send from an alias, the reply comes back to the alias and your provider delivers it to the inbox that owns it, so connecting that mailbox covers it.

Someone replied but my follow-ups kept going. Why?

Almost always because the reply landed somewhere WarmySender can't see. Follow-ups stop automatically only when we can see the reply arrive in the mailbox that sent the email. Three things to check: the sending mailbox has incoming (IMAP) access and not just outgoing; the reply actually came back to that mailbox rather than being read only in a forwarded copy or a shared inbox; and — if your campaign rotates across several mailboxes — that every one of them has incoming access, since each receives its own replies. Adding incoming access to the sending mailbox fixes it going forward, and you can stop an individual prospect by hand at any time from the campaign's Prospects tab.

Do I need to set incoming access up manually on Gmail or Outlook?

On a personal mailbox, no — signing in sets up both incoming and outgoing in one step. There is one exception worth knowing about, and it catches people out: if the mailbox is managed by an organisation on Microsoft 365 or Google Workspace, sending and reading are two permissions the administrator grants separately, and they can allow sending while leaving reading switched off. The sign-in still succeeds and the mailbox still sends, so nothing looks wrong — but nothing can be measured either, and your warmup results stay empty. If that is what you are seeing, read "Why can't WarmySender read my inbox?", which has the exact steps for an administrator to switch reading on. That page also covers the other case, which is worth knowing about: if you check and reading is already switched on, there is nothing further for you to change, and the right move is to email us with the mailbox address rather than to keep adjusting settings.

I use my own domain / a hosting provider. How do I add incoming access?

When you add the mailbox, fill in the incoming (IMAP) details alongside the outgoing (SMTP) ones. They're the same server address, username, and password you'd use to set the mailbox up in a mail app, and your provider lists them in their email-setup help. For providers other than Gmail and Outlook you normally use your regular mailbox password — no special app password is required. Once the incoming details are saved, warmup measuring, spam-rescue, and auto-stop-on-reply all switch on.

What does WarmySender do with incoming access to my inbox?

It uses incoming access only to run these features: checking whether warmup mail landed in the inbox or spam, moving warmup mail out of spam, and noticing when a prospect replies so your follow-ups can stop. It's focused on making warmup and your campaigns work well — it isn't there to read your personal correspondence, and the warmup and reply handling run quietly in the background.

Can I add incoming access later if I connected send-only first?

Yes. If a mailbox is connected outgoing-only, you can add the incoming (IMAP) details to it at any time — you don't need to remove and re-add it. As soon as incoming access is in place, warmup begins measuring and rescuing, and your campaigns begin auto-stopping on replies, with no further steps needed.

Related reading

• Why can't WarmySender read my inbox? — the exact steps to switch reading on when a Microsoft 365 or Google Workspace administrator has allowed sending but blocked it, and what to do when that permission turns out to be on already
• How email warmup ramps up — what to expect as your mailbox builds reputation over the first hour, day, and week
• Why warmup emails sometimes appear in your inbox — and how WarmySender tidies them away automatically
• Connecting mailboxes without app passwords — most providers connect with your normal mailbox password
• How follow-ups work in a campaign — the reply-aware follow-ups incoming access powers
• Your warmup dashboard — where inbox-vs-spam results appear per mailbox
• Full documentation — Cold Email, Email Warmup, LinkedIn, Instagram and Multichannel guides