Connect InboxKit Mailboxes to TrulyInbox in Under 4 Minutes

TrulyInbox runs one of the only genuinely free email warmup networks on the market, their forever-free plan lets you warm an unlimited number of mailboxes without paying a cent. InboxKit connects to TrulyInbox via email + password, pushes every selected mailbox into TrulyInbox's warmup network, and TrulyInbox's AI picks industry-specific conversation partners to simulate real inbox activity. No per-mailbox OAuth, no SMTP dropdown, no app password generation.

Total connect time is about 3 minutes. This is the path to pick if you don't want to pay for InboxKit's isolated warmup add-on at $3/mailbox/month and are OK sharing the warmup network with the rest of TrulyInbox's user base.

Most warmup products charge per-mailbox-per-month even for the network-only tier. TrulyInbox's forever-free plan gives unlimited mailboxes and unlimited warmup at $0. The trade-off is the shared pool: your mailbox is warming alongside every other TrulyInbox free user's mailbox, which can include senders with uneven sending habits.

TrulyInbox's own site lists the provider coverage explicitly: 'We support 18+ providers including Gmail, Google Workspace, Outlook.com, Office 365, Yahoo Mail, Zoho, iCloud, GoDaddy, Yandex, GMX, SendGrid, Mailgun, Amazon' (source). That's broader than most competitors but the free-tier pool is shared, which matters if you care about who your mailbox is 'talking to' during warmup.

Gather these:

Why IMAP matters for warmup. TrulyInbox's AI warmup works by sending warmup messages and then reading the replies to mark them as read, move them to primary, or flag as important. Without IMAP access, TrulyInbox can send but cannot read or interact with the inbox, which breaks the warmup signal. The TrulyInbox 'How It Works' page describes this: 'Sign in with Google or Microsoft OAuth. No passwords to share. For SMTP providers, just enter your credentials' (source). The InboxKit integration uses the SMTP credential path because it's the universal option across all 18+ providers TrulyInbox supports.

InboxKit already provisions SPF, DKIM, DMARC, and MX automatically. See email authentication explained if you want to verify manually.

The click path is a standard email + password flow:

Total: about 90 seconds.

You do not touch TrulyInbox's UI at any point during this connect. InboxKit handles the entire push, and the next time you log into TrulyInbox, the mailboxes will already be listed in your warmup queue.

Once pushed, TrulyInbox runs each mailbox through a 3-stage warmup pipeline:

TrulyInbox's AI picks industry-specific conversation templates based on the domain TLD and the sender name pattern. A mailbox on johnsdoctoroffice.com will get healthcare-adjacent warmup conversations; a mailbox on bobssaasventure.io will get SaaS-adjacent ones. This matters because Gmail's spam filter learns what 'normal' looks like for your domain. If the warmup traffic matches the expected industry, the model trains faster.

Do not run two warmup systems at once. If you already pay for InboxKit's isolated warmup add-on, disable TrulyInbox's warmup for that mailbox in TrulyInbox's settings. Running both roughly doubles warmup sent volume and confuses Google's reputation classifiers. See domain warmup best practices for the full trade-off.

TrulyInbox only handles warmup. It does not send your real cold email campaigns. You pair it with an outreach sequencer like Instantly, Smartlead, or Salesforge for actual sends. Use this ramp when you move a mailbox from warmup-only to real campaigns:

Google's practical cold email ceiling per mailbox is 40-50 per day regardless of warmup depth. To hit higher volumes, add more InboxKit mailboxes horizontally. See scale cold email 100 to 10000 for the mailbox-count math and email sending limits for the Google vs Microsoft limits.

One more footgun: TrulyInbox's free plan has a 'sharing penalty' because the network is shared, your mailbox will sometimes receive warmup mail from senders whose reputation is worse than yours. This is fine during ramp but becomes noise after day 30. If you're serious about deliverability, upgrade to InboxKit's isolated warmup add-on after the first month.

Run these three checks after every new TrulyInbox connect:

Test 1: Appears in TrulyInbox queue. Log into TrulyInbox → Mailboxes. Every InboxKit mailbox you pushed should be listed within 60 seconds with status 'Warming up'. If any are missing, the push silently failed, check the InboxKit Exports page for the error.

Test 2: 24-hour activity count. After 24 hours, check the Activity tab in TrulyInbox. You should see 5-10 sent, 3-8 received, 2-5 replied. If all counts are zero, either warmup is disabled on the mailbox or IMAP is broken.

Test 3: Inbox placement test. After 7 days of warmup, run a test via Mail Tester or GlockApps. You're looking for 8/10+. Anything lower means the warmup pool is not recovering your reputation fast enough, switch to isolated warmup. See inbox placement testing explained for full methodology.