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What is mailbox warmup and how it works in OutreachFox

Mailbox warm-up is the process of building a positive sending history for a mailbox before, and while, you use it for cold outreach. OutreachFox includes its own industry-tuned warm-up system: your…

Draft — written from product facts + domain knowledge; UI labels to be verified before publishing.

Mailbox warm-up is the process of building a positive sending history for a mailbox before, and while, you use it for cold outreach. OutreachFox includes its own industry-tuned warm-up system: your mailboxes exchange realistic emails with other mailboxes in the OutreachFox warm-up network, and those emails are opened, replied to, marked important and rescued from spam. Providers see wanted, engaged mail and rate the mailbox accordingly.

Why it is needed

Gmail and Microsoft assign every sending address and domain a reputation. A new address has none, and a new domain is treated with suspicion. If the first thing a mailbox does is send 50 unsolicited emails a day, the provider classifies it as a spam source within days and the mailbox is effectively burned. Warm-up front-loads the good history so campaign mail arrives from a known, trusted sender.

How OutreachFox warm-up works

  1. Warm-up network. All mailboxes with warm-up enabled form a private pool. Your mailbox sends to and receives from other real mailboxes across Google, Microsoft and other providers — not from a single test server.
  2. Realistic conversations. Warm-up emails are threaded, varied, human-length messages with subjects and replies. They do not contain marketing content or links.
  3. Engagement actions. Receiving mailboxes open the email, reply to a percentage of them, and if a message landed in spam, move it to the inbox and mark it not spam. This is the signal that repairs reputation.
  4. Ramp-up. A warm-up profile controls volume: start at a few emails a day and increase daily until the max is reached (usually 10–14 days). See Create and customise a warmup profile.
  5. Provider-specific tuning. The four default profiles (Custom Mailboxes, Azure, Microsoft, Google) apply different ramps because each provider tolerates volume differently.
  6. Continuous monitoring. The mailbox's Warm up tab reports health score, inbox placement, spam placement, bounce rate, daily send/reply history and an ESP breakdown.
  7. Runs alongside campaigns. Warm-up keeps going after launch at a reduced level, so engagement signals keep flowing while campaign mail — which gets far fewer replies — goes out.

Where you control it

**Task****Path**
Turn on**Mailbox** → select mailboxes → **Enable Warm Up** → choose profile → **Enable Warmer**
Change or create a profile**Settings** (bottom-left) → warm-up profiles, or **Manage Profiles** in the Enable Warm Up dialog
Bulk enable/disable**Mailbox** → select all → bulk actions → **Warm Up** → **Enable** / **Disable**
See stats**Mailbox** → mailbox → **Warm up** tab

What warm-up does not do

  • It does not fix missing SPF, DKIM or DMARC. Authentication must be in place first.
  • It does not repair a blacklisted domain. Check blocklists separately.
  • It does not make bad lists or spammy copy deliverable. Warm-up protects reputation; campaigns spend it.

Timeline

**Day****What happens**
0Mailbox connected, warm-up enabled, 3–5 emails sent
1–7Volume ramps +2–3/day; placement stabilises; health score appears
7–14Volume reaches 30–40/day; check health, placement, ESP breakdown
14+Add to campaign at 20–30 emails/day; switch to a reduced warm-up profile
21+Raise campaign limit to 40–50/day if bounce \<3% and spam placement \<5%

FAQ

  • Can recipients see warm-up emails? No. Warm-up emails only go to other warm-up network mailboxes. OutreachFox files them out of the way in the receiving mailbox.
  • Does warm-up count against my campaign limit? No. Campaign emails per day and warm-up emails per day are separate settings.
  • Should I ever turn it off? Only when retiring a mailbox. Keep it on at reduced volume for as long as the mailbox sends campaigns.

Related articles

  • Enable warmup on your mailboxes
  • Create and customise a warmup profile
  • Warmup best practices: how long, how fast, and when to launch
  • Read the warmup health dashboard
  • Troubleshooting warmup (paused, low health score, high spam placement)
  • Deliverability fundamentals for cold email

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More in Warmup

Enable warmup on your mailboxes→Create and customise a warmup profile→Read the warmup health dashboard (health score, inbox vs spam placement, bounce rate)→Review warmup send/reply history and ESP breakdown→Warmup best practices: how long, how fast, and when to launch→Troubleshooting warmup (paused, low health score, high spam placement)→