How often should you validate your email list?

Email lists decay at roughly 2–3% per month. That means a 100,000-contact list loses around 2,500 valid addresses every 30 days. Here's a validation cadence that fits different business types.

Email addresses don't expire with an announcement. People change jobs, abandon personal accounts, switch to new email providers, and let old addresses lapse — all without telling the senders they've subscribed to. Research consistently shows list decay of 2–3% per month, which means a 100,000-contact list loses roughly 30,000 valid addresses per year through natural attrition alone.

The baseline: validate before every major campaign

If you only follow one rule, make it this: run a bulk validation pass on any segment that hasn't received an email in the last 90 days before sending to it again. A 90-day gap is long enough for a non-trivial number of addresses to have gone stale. The cost of one bulk validation job is always less than the cost of a bounce-related ESP suspension.

Cadences by business type

• High-frequency senders (weekly or more): validate new sign-ups in real time; bulk validate full list quarterly
• Moderate senders (monthly): validate new sign-ups in real time; bulk validate before each new campaign
• Low-frequency senders (quarterly or less): validate the entire list before every single send
• Dormant lists (haven't sent in 6+ months): validate the full list before re-activating; expect 15–30% decay

New sign-ups are different

Real-time validation at the point of sign-up should always be on, regardless of your send frequency. A bad address is better caught at the form than discovered as a hard bounce three months later when you finally send a campaign. Real-time validation is your first line of defence; bulk validation is your second.

What about transactional email?

Transactional emails (receipts, password resets, notifications) should always be sent — even to addresses of uncertain validity — because the user triggered the action and expects the email. However, if a transactional email hard-bounces, suppress the address immediately and flag the account for attention. The user may need to update their email address.