one of the biggest mistakes i see: agencies going all-in on Google or all-in on Outlook.

single-provider setups collapse when that provider updates its filtering models. i watched it happen in late 2025 when Google dropped new deliverability policies. agencies that were 100% Google got wiped overnight. campaigns that had been working for months suddenly hit 100% spam rates.

i call it the Two-Lane Provider Strategy. you split your sending infrastructure between Google Workspace and Microsoft 365 (Outlook), so when one provider tightens its filters, your other lane keeps running.

the two split configurations

configuration 1: the 70/30 split (recommended for most teams)

Provider Volume Share Best For
Google Workspace 70% B2B audiences on Gmail/Google Workspace
Microsoft 365 30% Corporate audiences on Outlook/Exchange

use this when your ICP is primarily Gmail-based (startups, agencies, tech companies). Google handles the bulk, Outlook provides the safety net.

configuration 2: the 50/50 split (recommended for enterprise targets)

Provider Volume Share Best For
Google Workspace 50% Mixed audiences
Microsoft 365 50% Even distribution of risk

use this when your ICP includes larger companies where Outlook/Exchange is the default. equal distribution means neither provider carries disproportionate risk.

how to implement

  1. buy domains in pairs. for every sending domain, register two lookalikes. assign one to Google, one to Outlook.
  2. warm both lanes simultaneously. don't warm Google first and add Outlook later. run both from day one.
  3. monitor each lane independently. your Google deliverability metrics and Outlook metrics should be tracked separately. a problem on one lane doesn't mean both are failing.
  4. if one lane degrades, shift volume. temporarily move 80-90% of sending to the healthy lane while you diagnose and fix the other.

domain naming convention

your sending domains should look like legitimate business domains that a real company would own.

if your main domain is premiuminboxes.com, good lookalikes would be domains like getpremium or premium-team because they look like legitimate brands that a real company might own.

on the other hand, domains like premiumoffer123 or premium-outreach-mail are obvious red flags because providers check domain patterns and will treat anything that looks disposable as suspicious.

implementation checklist