Symptoms#
- Messages landing in spam despite previously good placement
- Bounces mentioning policy, authentication, or reputation
- Provider dashboards showing a drop in reputation or authentication pass rate
Diagnosis steps#
- Confirm the configuration is live: query DNS from an external resolver and check the sending platform's settings page.
- Send to a seed mailbox and read the full headers, especially Authentication-Results.
- Compare the domains in From, Return-Path, and DKIM d= for alignment.
- Check provider dashboards (Google Postmaster Tools, Microsoft SNDS) for reputation and error rates.
- Review recent changes: new vendors, DNS edits, list imports, volume spikes.
Likely causes#
- Sending cold mail from the primary company domain.
- Skipping DMARC on secondary domains because 'they do not matter'.
- Buying aged domains with unknown history.
Fix and re-verify#
- Register 2 to 5 lookalike domains and redirect them to your main site.
- Set up SPF, DKIM, and DMARC on every domain from day one.
- Create 2 to 3 mailboxes per domain and warm each for 3 to 4 weeks.
- Cap sends at 30 to 50 per mailbox per day and rotate across mailboxes.
- Monitor bounce and reply rates per mailbox; retire any that degrade.
Frequently asked questions#
How many emails can I send per mailbox per day?
Google Workspace allows 2,000, but for cold outreach 30 to 50 keeps you under behavioral thresholds.
Should I use Google Workspace or Microsoft 365 for cold email?
Both work. Workspace mailboxes tend to warm faster; Microsoft has stricter outbound spam filtering.