How to connect a Gmail or Google Workspace alias to WarmySender

Overview

WarmySender helps teams run cold email campaigns, warm up their mailboxes, automate LinkedIn outreach, and coordinate multichannel sequences from one dashboard. This guide walks through connecting a Gmail or Google Workspace alias-domain address — a common setup where you send from one address (e.g. [email protected]) but the inbox is actually owned by a different primary Google account (e.g. [email protected]).

Alias setups are the most error-prone Gmail variant to connect because they introduce two addresses (primary + alias), two settings (server hostnames + per-user "Send mail as" routing in Gmail), and one specific Google requirement (App Passwords instead of your regular login password). This page covers every step end-to-end and calls out the two typos almost everyone makes.

What is a Workspace alias?

A Google Workspace mailbox has a single primary address (the one you sign in with) and can have additional addresses that all deliver to the same inbox. Those additional addresses are called aliases. Two flavours exist:

• Alias domain. Your Workspace admin added a whole second domain (e.g. yourbrand.com) to your Workspace. Every user automatically gets a matching address on the new domain — so [email protected] also receives mail addressed to [email protected].
• Per-user alias / "Send mail as". An individual user adds an additional address in Gmail Settings › Accounts › Send mail as. The address can be on a domain you own, on an alias domain, or even on a separate Workspace mailbox.

Either way, the inbox you actually sign in to is the primary address, and the alias is just a label that mail can be addressed to and sent from. WarmySender supports both flavours — the connect form is the same.

Concrete example used throughout this guide:

• Primary address (the one you sign in to): [email protected]
• Alias address (the one you want to send from and warm up): [email protected]

Before you start — Google Workspace setup

Do these four steps on the Google side before you open the connect form in WarmySender. The whole sequence takes about five minutes.

1. Turn on 2-step verification on your primary Google account. Google will not let you generate an App Password unless 2-step verification is on. Visit myaccount.google.com/security, sign in as the primary account, and follow the 2-step verification setup if it isn't already on. If you use a Workspace account where the admin manages this, ask them to enable it for you.
2. Generate an App Password for your primary account. Go to myaccount.google.com/apppasswords. Type a name like WarmySender and click Create. Google shows you a 16-character password in groups of four (e.g. abcd efgh ijkl mnop). Copy it now — Google will not show it again. You can paste it with or without spaces — we remove them for you. If the connection still fails, the password is not the problem: check the sign-in address and your Workspace admin settings below.
3. Confirm the alias exists in Workspace. If your team set up an alias domain, the alias already exists for every user — you can skip ahead. If you're using a per-user "Send mail as" alias, ask your Workspace admin to confirm the alias was added in Admin Console › Directory › Users › your user › User information › Email aliases. The alias takes a minute or two to propagate.
4. (Optional, per-user alias only) Add the alias in Gmail's Send mail as. If you want to manually send from the alias in Gmail's web interface too, open mail.google.com, click the gear icon, choose See all settings, open the Accounts tab, and click Add another email address next to Send mail as. Add the alias, verify it via the link Google emails you, and pick Treat as an alias. This step is optional for WarmySender — the platform sends directly through SMTP and does not depend on Gmail's Send-as configuration — but most teams want both surfaces working.

Connecting in WarmySender

Once you have your App Password and the alias is confirmed, open WarmySender, go to Mailboxes › Connect Mailbox, and pick Custom IMAP / SMTP (App Password). Fill in the form with the values below.

Server settings

Use these exact values. The hostnames have gmail in them, not google — see Common mistakes below for why this matters.

Step-by-step

1. Open Mailboxes in WarmySender and click Connect Mailbox.
2. Choose Custom IMAP / SMTP (App Password) as the connection type.
3. In the Email address field, type the alias you want to warm up and send from (e.g. [email protected]).
4. In the Username field, type your primary Google address (e.g. [email protected]). This is the most-missed step — see Common mistakes.
5. Paste the App Password into the Password field. You can paste it with or without spaces — we remove them for you, so both abcd efgh ijkl mnop and abcdefghijklmnop work.
6. Leave the server fields pre-filled. If anything looks different from the table above, correct it.
7. Click Test connection. WarmySender will probe both SMTP and IMAP and show you a green check on each within a few seconds. If anything fails, see Troubleshooting.
8. Click Save. The new mailbox appears in your list with a green Connected badge and is immediately eligible for warmup and campaign use.

Common mistakes (read this — it'll save you 10 minutes)

Don't use smtp.google.com or imap.google.com

The real Gmail server addresses are smtp.gmail.com and imap.gmail.com — with gmail, not google. smtp.google.com and imap.google.com are not real hostnames; nothing answers there. This is the single most common typo we see, especially when copying values from old setup tutorials. WarmySender's connect form catches this exact typo and offers a one-click fix that swaps google for gmail in both fields, but it's much faster to type the right value the first time.

Don't put the sending server in the receiving field

Gmail uses two different server addresses, and it matters which one goes where:

The mistake to avoid is putting smtp.gmail.com in both boxes — usually by leaving the incoming field blank and assuming it will follow the outgoing one, or by copying the same value twice. That combination looks completely fine when you save it: the mailbox connects, and your campaign emails go out normally. What quietly doesn't happen is receiving. Warmup can't confirm whether your emails reached the inbox or the spam folder, it can't rescue anything from spam, and campaign follow-ups won't stop automatically when someone replies — so the mailbox can sit for weeks looking healthy while its warmup score never moves.

You shouldn't have to think about this: WarmySender fills in both server addresses for you as soon as it recognises your provider, and if a sending address ever ends up in the incoming field we correct it and tell you what we changed. If you're filling the form in by hand, the shortcut to remember is smtp = send, imap = inbox.

One exception worth knowing: some business and self-hosted setups genuinely use a single address — often something like mail.yourcompany.com — for both sending and receiving. That's a valid configuration and WarmySender leaves it exactly as you entered it. The rule above applies to the big providers (Gmail, Google Workspace, Outlook, Zoho, Yahoo and similar), which always split the two.

Don't connect a send-only service for warmup

Bulk sending services — the kind you'd use to fire transactional email from an app — can deliver mail but have no inbox behind them. There is nothing to receive into, so there's no incoming server to enter and no way for warmup to prove where your messages landed. If you use one of these to send, connect the real mailbox for that address in WarmySender instead: the one you actually sign in to and read. WarmySender will tell you plainly if it spots a send-only service on a mailbox you're connecting.

Don't put the alias address in the Username field

This trips up almost every first-time alias setup. The Username for SMTP and IMAP must be your primary Google account — the one that owns the App Password. Gmail authenticates the App Password against the primary account, not the alias. Putting the alias address in the Username field results in an authentication failure even though the password is perfectly correct.

The right mental model: username = who's signing in, From = who the message looks like it's from. They are different fields by design and they're supposed to be different values for alias mailboxes.

Don't use your regular Google login password

Even with 2-step verification turned on, Gmail will reject your regular login password on SMTP and IMAP. You must generate a 16-character App Password and use that. If you see "Authentication failed" on the test, this is almost certainly the cause — double-check you pasted the 16-character App Password, not your day-to-day Google password. Spaces are never the issue — we remove them for you either way.

Don't skip 2-step verification

The App Password page won't appear in your Google account settings until 2-step verification is enabled. If myaccount.google.com/apppasswords shows you a message about needing 2-step verification, that's the cause — turn it on first, then come back.

If your Google Workspace administrator manages the account

On a company Google Workspace account, some of the settings this guide relies on belong to your administrator rather than to you. That matters because Google gives the same "Authentication failed" message whether the password is wrong, the sign-in address is an alias instead of the primary account, or your organisation has switched off the access this connection needs. So if one mailbox on your domain connects fine and another keeps failing with a password you know is correct, ask your administrator to check these four things.

1. Users must be allowed to turn on 2-Step Verification. In the Google Admin console, under Security › Authentication, 2-Step Verification has to be available to the user (or already enforced). App Passwords only exist on an account that has 2-Step Verification on, so if the organisation blocks it, the App Password page never appears.
2. IMAP has to be enabled for the user. In the Admin console, under Apps › Google Workspace › Gmail › End User Access, the IMAP setting should be on — the option usually reads something like "Enable IMAP access for all users". Also check that the setting isn't switched off for the specific organisational unit or group the user sits in: Workspace settings are inherited, so one team can be restricted while everyone else is fine. Without incoming access, warmup can't confirm where your mail landed and replies can't be detected.
3. "Less secure apps" is gone — App Passwords are the supported path. Google retired that old toggle, so there is nothing to switch on there any more. If an older internal runbook still points at it, the current answer is: turn on 2-Step Verification and use a 16-character App Password, exactly as described above.
4. After any admin change, generate a new App Password and reconnect. An App Password created before the setting was changed will usually keep failing. Create a fresh one at myaccount.google.com/apppasswords, then open the mailbox in WarmySender and reconnect with the new value. Admin changes can take a few minutes to reach every account, so if the first attempt still fails, wait a moment and try once more.

Menu names in the Google Admin console change from time to time; if the exact wording differs from the above, look under Security › Authentication for the 2-Step Verification policy and under the Gmail app's end-user access settings for IMAP.

How warmup uses your alias

Once connected, your alias mailbox starts receiving warmup messages from the WarmySender peer network on day one (a small number, ramping up over 4-6 weeks as your sender reputation builds). Those messages are addressed to your alias, but because Workspace delivers alias mail to your primary inbox, they arrive there. WarmySender's scanner identifies the warmup messages by a hidden tag in the subject line and archives them automatically so they don't clutter your day-to-day view.

You don't need to configure anything extra for warmup to work with the alias. The same flow handles cold email campaigns: when WarmySender sends a campaign email from your alias, the message is authenticated against the primary account (which has the App Password) and the From header carries the alias address. Recipients see the message coming from your brand domain, and when someone replies, their reply comes straight back to that same alias address — which Workspace delivers into your primary inbox, exactly like the warmup mail above. You don't need to fill in a reply-to address for this: unless a step names a different one, replies come back to the address the campaign sent from.

For more on how warmup ramps up across your first hour, first day, and first week, see How warmup ramps up.

Troubleshooting

Test connection fails with "Authentication failed"

Google sends the same message for several different situations, so work down this list in order:

1. The Username field has the alias address instead of the primary account. Change it to the primary Google address that owns the App Password — see the alias-as-username mistake above. This is the most common cause on Workspace domains, and it looks exactly like a wrong password.
2. You pasted your regular login password instead of the App Password. Regenerate the App Password at myaccount.google.com/apppasswords and paste the 16-character value (with or without spaces — we remove them for you).
3. 2-step verification is off on the primary account. Turn it on at myaccount.google.com/security and regenerate the App Password.
4. Your Google Workspace administrator has switched off the access this needs. If one mailbox on your domain connects and another doesn't, this is usually why — see If your Google Workspace administrator manages the account.

Spaces are not on this list: you can paste the App Password with or without them, because we remove them for you.

Do I need my Google Workspace administrator to change anything?

Sometimes. On a personal Gmail account, no — everything is in your own account settings. On a company Google Workspace account, your administrator controls whether users may turn on 2-Step Verification (which App Passwords require) and whether IMAP is enabled for your account, and either one being off produces the same "Authentication failed" message as a wrong password. The full checklist to send them is in If your Google Workspace administrator manages the account. After any change on their side, generate a new App Password and reconnect.

Test connection fails with "Could not connect to server"

You almost certainly typed smtp.google.com or imap.google.com instead of smtp.gmail.com and imap.gmail.com. Swap google for gmail in both hostname fields. WarmySender's connect form usually catches this and offers a one-click fix; if you somehow bypassed that, fix it manually and click Test connection again.

Why is the username different from the email address?

By design. Gmail authenticates the App Password against the primary Google account that owns it — so the SMTP/IMAP Username is always the primary address. The From address (what recipients see) is your alias. For non-alias mailboxes (where the primary and the send-from address are the same), Username and Email address are the same value. For alias mailboxes, they're different by design.

Workspace says the alias isn't recognised

Either the alias hasn't been added in Workspace yet, or it was added in the last minute or two and hasn't propagated. Ask your Workspace admin to confirm the alias is listed in Admin Console › Directory › Users › your user › Email aliases (for per-user aliases) or that the alias domain is added in Domains (for alias-domain setups). Wait a minute or two and try the test again.

My alias is a "Send mail as" address, not a Workspace alias-domain. Does that work?

Yes. WarmySender treats any address you can send from in Gmail's Accounts settings the same way. The setup is identical: primary Google address as Username, App Password in the password field, alias address in the From field. Make sure you completed Google's verification step when you added the Send-mail-as address (Google emails a code or confirmation link to the alias address; you click it to verify).

Can I warm up multiple aliases on the same Workspace account?

Yes. Connect each alias as a separate mailbox in WarmySender. Each connection uses the same Username (your primary Google account) and the same App Password, but a different From address (a different alias). Each mailbox gets its own warmup ramp, daily limit, and sender reputation.

I'm getting a bounce notice from Google when I send

If the bounce mentions "Address not found" or "recipient does not exist", the recipient address is the issue — re-check the lead list. If the bounce mentions "daily sending limit exceeded", you hit Gmail's per-day cap (consumer Gmail is 500/day; Workspace is 2,000/day) — split your sending across multiple mailboxes or slow the campaign. If the bounce mentions "authentication failed" on later sends after a successful Test connection, your App Password may have been revoked (Google revokes them on certain account events like password changes or admin policy changes) — regenerate the App Password and update the mailbox in WarmySender.

Can I connect Gmail without an App Password?

No — Gmail and Google Workspace mailboxes connect with an App Password over IMAP/SMTP, for both primary and alias addresses. Turn on 2-step verification, generate a 16-character App Password, and paste it into the connect form as described above. (Microsoft 365 and Outlook work differently: a standard Microsoft mailbox can connect with one-click Sign in with Microsoft, and Microsoft aliases connect the same way this page describes — see connect a Microsoft 365 alias.)

Where do I generate an App Password?

myaccount.google.com/apppasswords. You must be signed in as the primary Google account and have 2-step verification turned on. Name it WarmySender (or anything memorable), click Create, copy the 16-character value Google shows you. Google does not show the password again, so save it somewhere safe before closing the dialog.

Why does WarmySender need IMAP access?

IMAP is how we read your inbox to detect replies (so we can pause a campaign step when someone replies to your cold email), recognise warmup messages and archive them out of your day-to-day view, and track bounces. We only read messages relevant to your outreach activity; we never read or store the contents of personal email. Without IMAP, replies and warmup recognition wouldn't work.

How long does warmup take to start?

Warmup begins on day one with a small number of messages (typically 1-2 sends and a handful of receives in the first hour, ramping to 3-5 each by end of day one). Full target volume (default 40/day, configurable) is reached at around day 14 for a healthy mailbox. The slow ramp protects your sender reputation — a brand-new mailbox suddenly sending 50 messages an hour looks identical to spam to receiving providers. See How warmup ramps up for the full curve.

If your mailbox says it needs reconnection

If a mailbox that used to work suddenly shows "needs reconnection", it almost always means the saved App Password no longer works. The most common reasons are:

• The App Password was changed or deleted in your Google account.
• Your account password was reset (Google revokes App Passwords when the main password changes).
• 2-Step Verification was turned off and back on, or otherwise reset, which invalidates older App Passwords.

In every case the fix is the same: generate a fresh App Password and paste it in. You do not need to delete the mailbox or change any server settings.

How to reconnect (about two minutes)

1. Go to myaccount.google.com/apppasswords, signed in as your primary Google account. Type a name like WarmySender, click Create, and copy the new 16-character App Password (shown in groups of four, e.g. abcd efgh ijkl mnop). Google won't show it again, so copy it before closing the dialog.
2. In WarmySender, open Mailboxes, find the mailbox that needs attention, and click Reconnect.
3. Paste the new 16-character App Password into the password field. Use the App Password — not your normal Google login password. You can paste it with or without spaces — we remove them for you, so both abcd efgh ijkl mnop and abcdefghijklmnop work.
4. Leave the email address (your primary Google account as the username) and the server settings exactly as they are — only the password changed.
5. Submit. WarmySender checks the new password against your inbox right away. When it passes, the mailbox returns to Connected and warmup resumes automatically.

Using Microsoft or Outlook instead?

It depends on how that mailbox was connected, and the two answers are different:

• If you connected it with “Sign in with Microsoft” — the usual way — there is no password to regenerate, and creating an App Password will not help. Click Reconnect on the mailbox and sign in with Microsoft again. That is the whole fix and it takes about a minute.
• If you connected it with an App Password, generate a fresh one from your Microsoft account security page, click Reconnect, and paste the new App Password in. Keep the email address and server settings unchanged.

Not sure which you used? Start with Reconnect and only generate an App Password if you are actually asked for one.

Why did it say connected and then need reconnecting again?

The password is checked at the moment mail is actually sent, not just when you save it. So if the App Password is wrong — for example, you pasted your normal Google password by mistake, or the App Password was revoked — the mailbox can briefly look connected and then show as needing reconnection again on the next send. Pasting a freshly generated 16-character App Password as described above clears it for good.

Related guides

• Full documentation — every WarmySender guide in one place
• Connect a Microsoft 365 alias — the Microsoft equivalent of this guide: several aliases on one licensed mailbox, each its own sender
• Connect a Microsoft 365 mailbox — connecting a standard (non-alias) Microsoft mailbox, with Sign in with Microsoft, App Password, and Custom IMAP/SMTP methods
• Bulk import mailboxes (CSV + paste) — connect many alias mailboxes at once
• How warmup ramps up — what to expect in your first hour, first day, first week
• Provider-side blocks — what to do if Gmail throttles your sending
• Cold email campaigns — set up your first campaign once your alias is connected
• Email warmup — what warmup is and why every new mailbox needs it
• LinkedIn outreach — the LinkedIn channel of the WarmySender platform
• Support — email [email protected] if you're stuck