How Many Emails Can You Send Before Being Considered Spam?

Every outreach team eventually faces the same question: Are we sending too many emails? 

It’s a valid concern, but also the wrong one. There’s no universal number that triggers spam filters.

Mailbox providers don’t penalize senders for volume alone. They evaluate patterns in your sending behavior and how recipients respond. 

If you’re reaching 10 million engaged, opt-in subscribers, sending at scale is perfectly acceptable. But if you send 80 cold emails to disinterested contacts and trigger a few spam complaints, your domain reputation can plummet overnight. 

In this guide, we’ll break down:

• How mailbox providers actually define spam
  
  
• Sending limits across Gmail, Outlook, and other major providers
  
  
• How to safely warm up new inboxes for cold outreach
  
  
• Early warning signs you’re sending too many emails
  
  
• Tools to diagnose and fix deliverability issues

If you’re planning to scale outreach, start with a quick email spam test. It’s the easiest way to understand how mailbox providers currently view your domain before you increase volume.

How Mailbox Providers Evaluate Sender Reputation

Spam filters rely on several signals to evaluate your reputation. The three biggest factors are recipient engagement, complaint rates, and list quality.

Engagement signals

Mailbox providers track behavioral data like your email open rates, clicks, and response times across your email sends.

Positive actions such as opens, replies, and “Not Spam” markings improve your sender reputation, while ignored or deleted emails lower it.

Run an automated email warm-up before scaling email sends to build real engagement signals 

Complaint rate thresholds

Report Spam clicks are one of the strongest negative indicators. Even small spikes can cause filtering.

• <0.1% = Good
  
  
• 0.3%+ = Red flag territory (Source: Google Workspace Sender Guidelines)
  
  

Keep complaint rates low by maintaining clean lists, personalizing messages, and avoiding sudden jumps in volume.

Bounce Rates and List Hygiene

High bounce rates suggest poor targeting or outdated lists. Both hurt reputation.

• Keep hard bounces below 2%.
  
  
• Verify addresses regularly and avoid scraped or purchased lists.

Strong list hygiene indicates to email providers that your sending practices are compliant and well-managed.

Email Sending Limits: Provided Permits & Policies

(These apply primarily to B2B senders using Gmail, Outlook, and similar platforms.)

Note: These are upper limits, not targets. Cold outreach should stay well below these limits until your domain is warmed up. Read more on how to keep your emails out of spam.

How to Determine Safe Sending Volumes for Cold Email Outreach

Cold outreach and bulk email are not the same because email service providers treat them very differently.

Cold email relies on trust, not volume. You’re sending to people who don’t yet know you, which means every interaction is under closer scrutiny.

The safest approach is to scale your sending gradually:

Recommended sending schedule

‍

• Week 1: 10–20 emails per day
  
  
• Week 2 & beyond: Increase by 10–20 per week
  
  
• Steady state: 50–100 emails/day per inbox (after warm-up)
  
  

If you’re managing larger campaigns, spread volume across multiple inboxes or domains. This builds resilience and prevents sudden spikes that can trigger spam filters.

Positive engagement signals inbox providers that your domain is trustworthy. That’s why the warm-up phase is an ongoing process. Keep it active before, during, and between campaigns to maintain steady engagement patterns like opens, replies, and “Not Spam” marks. This consistency helps preserve your sender reputation as you scale.

Always authenticate your sending setup with SPF, DKIM, and DMARC to prove identity and improve inbox placement.

Signs You’re Sending Too Many Emails

When you scale outreach too quickly, your deliverability signals start to degrade before performance metrics sharply decline. Watch for these early warning signs:

• Sudden drop in open/reply rates: your emails are likely being filtered or throttled.
  
  
• Higher bounce rates or unsubscribes: your list quality or copy needs a review.
  
  
• Spam complaints or delivery errors: these are the strongest indicators that your sender reputation is deteriorating.

You don’t need to send thousands of emails to trigger these patterns, even small B2B volumes can indicate problems if engagement drops.

Check deliverability weekly using tools that analyze real outreach data:

• Start with MailReach’s email warmer. Your Reputation Score there is the clearest early signal of how mailbox providers view your domain. If that score starts to drop, your sender reputation is already slipping and needs attention.
  
  
• Run MailReach’s email spam tester to determine whether messages land in Primary, Promotions, or Spam.
  
  
• Review trends in Google Postmaster Tools or Microsoft SNDS if you’re sending at higher volumes (Note: Postmaster is generally useful only once you reach thousands of daily emails).

Engagement-based triggers

If reply or open rates decline while sending volume increases, you are scaling too quickly. Deliverability algorithms interpret reduced engagement as a signal to filter, often before senders reach technical limits. 

Note: If engagement is slipping, pause new sends and run a spam test. This is the fastest way to determine whether your domain requires remediation before continuing outreach. 

How to Fix Emails Landing in Spam

If deliverability drops, pause sending immediately to limit damage. Follow these recovery steps:

• Pause sending immediately. Don’t continue pushing campaigns, it worsens reputation loss.
  

• Run a MailReach spam test to see your current inbox placement and identify potential content or authentication issues. Check for sudden volume jumps, poor engagement, or policy violations.
  

• Assess your sender reputation by using MailReach’s email warm-up to monitor your Reputation Score. A declining score means your domain trust is eroding, so continue warm-up cycles to rebuild positive engagement before resuming new sends.

• Review compliance: follow CAN-SPAM, GDPR, and CASL rules.
  

• Always include a clear and functional unsubscribe link.
  

• Do not use misleading subject lines.
  

• Honor opt-outs within 10 days.
  

• Clean your list: remove inactive, bounced, or unverified contacts. Avoid using purchased lists.

Read more on how to identify invalid emails and bad leads.

If your domain reputation is severely damaged, switch to a new domain and restart with a gradual warm-up schedule, while ensuring you resolve root causes and do not reintroduce the same issues

Deliverability Wins, Not Volume

There’s no universal number that defines spam, only patterns of engagement that build or erode trust. 

Two founders can send the same number of emails with opposite results: one lands every message in the inbox, the other ends up in spam. The difference is their domain reputation.

The best senders think long-term:

• Inbox > Reach: prioritize placement over raw output.
  
  
• Reputation > Speed: consistent trust beats rapid scaling.

If you’re scaling outreach, make deliverability your first KPI. Start with an email warm-up, run an email spam test, and monitor your domain health before increasing volume.

Your pipeline depends on it. Do not scale without these checks.   

Ready to scale safely? Run an email warm-up before launching your next cold outreach campaign. It builds your sender reputation automatically, so your first 100 sends land where they should.