Short answer: for cold email to reach the inbox, do four things: use a separate sending domain; configure SPF, DKIM and DMARC correctly; warm up new domains and mailboxes gradually; and keep volume per mailbox low, emailing only verified, precise lists with an easy way to unsubscribe.
Why deliverability matters so much
Many teams blame low outbound replies on copy when the emails never reached the inbox. Mailbox providers decide between inbox and spam based on the sending domain's reputation, its authentication and how recipients react.
Since 2024, Google and Yahoo have applied stricter requirements to bulk senders, and Microsoft's Outlook followed. They include email authentication, easy unsubscribing and keeping spam complaint rates very low.
Step 1: set up a separate sending domain
Do not send cold email from your main company domain. If its sending reputation suffers, your everyday business email, such as invoices and notifications to customers, suffers too.
A common approach is a similar domain: if your main domain is example.ai, send from getexample.ai or example-mail.ai, and redirect that domain's website to your main site so recipients see a normal company website.
Step 2: configure the three authentication records
| Record | What it does | Check |
|---|---|---|
| SPF | Declares which servers may send for your domain | One SPF record per domain; merge multiple services into one |
| DKIM | Signs emails to prove they were not altered | Generate it in your email provider and add it to DNS |
| DMARC | Tells receivers what to do when checks fail and sends you reports | Start in monitoring mode, then tighten once everything passes |
Afterwards, send a test email to a free authentication checker and confirm all three pass.
A common mistake is two SPF records on the same domain, which makes SPF fail. If you use several sending services, merge them into one record.
Step 3: warm up
New domains and mailboxes have no history, and sudden volume looks like spam. To warm up:
- Use the mailbox for normal two-way email for the first weeks, starting with very low volume.
- Increase daily volume gradually.
- Warm-up tools can help, but they do not replace real conversations with replies.
Step 4: control volume and list quality
- Spread volume: use several mailboxes and keep daily volume per mailbox low.
- Verify addresses: high bounce rates badly hurt reputation.
- Precise lists: emailing irrelevant people brings spam complaints. See How to define an ICP.
- Plain text style: minimize images, tracking pixels and links in cold emails.
- Offer an opt-out: include a clear way to unsubscribe and honor it promptly. Many countries require it by law; see B2B outbound for AI agents.
Step 5: monitor continuously
- Use Google Postmaster Tools to watch domain reputation and complaint rates.
- Read DMARC reports regularly to spot anyone spoofing your domain.
- When replies suddenly drop, first test whether emails still reach the inbox.
FAQ
Can we send cold email from personal Gmail or Outlook accounts?
Not recommended. Use authenticated mailboxes on a company domain. Sending business email from personal accounts looks unprofessional and is more likely to be restricted.
How long does warm-up take?
It depends on domain history and sending plans; usually several weeks of gradually rising volume. Slower is safer.
Should DMARC start at reject?
Start in monitoring mode (p=none) to collect reports. Once every legitimate sending source passes, tighten step by step to quarantine or reject.