Bulk Sending

Guidelines and best practices for sending email at scale while maintaining high deliverability and protecting your domain reputation.

Authentication Required

Ensure SPF, DKIM, and DMARC are all properly configured and passing before sending any bulk email. Gmail and Yahoo require bulk senders (5,000+ emails/day) to have all three authentication methods in place.

IP & Domain Warmup

New IPs and domains have no sending reputation. Sudden spikes in volume from a new IP trigger spam filters. You need to gradually build your sending reputation.

Warmup Schedule

Week 1

50–100 emails per day

Week 2

200–500 emails per day

Week 3

1,000–2,000 emails per day

Week 4+

Gradually increase to full volume

Send to your most engaged recipients first during warmup. Positive engagement signals (opens, clicks, replies) build your reputation faster.

Best Practices

Use a Dedicated Sending Subdomain

Instead of sending marketing emails from yourdomain.com, use a subdomain like mail.yourdomain.com or news.yourdomain.com. This isolates your bulk sending reputation from your primary domain.

One-Click Unsubscribe

All bulk and marketing emails must include a visible unsubscribe link. Gmail and Yahoo require the List-Unsubscribe-Post header for one-click unsubscribe support. Airsend automatically adds these headers when you use the bulk sending feature.

Monitor Rates

Keep hard bounce rate below 2%
Keep spam complaint rate below 0.1% (1 per 1,000 emails)
Exceeding these thresholds will cause providers to throttle or block your emails

Content Guidelines

Avoid spam trigger words in subject lines (e.g., "FREE", "ACT NOW", "WINNER")
Maintain a healthy text-to-image ratio — do not send image-only emails
Include your physical mailing address (CAN-SPAM, GDPR requirement)
Personalize messages when possible — generic blasts are more likely to be flagged
Spread your sends over time — do not blast your entire list at once

Mailing Lists

Maintaining clean mailing lists is critical for deliverability and sender reputation.

List Hygiene

Remove invalid email addresses and hard bounces regularly
Use double opt-in for new subscriptions to ensure addresses are valid
Remove inactive subscribers who haven't engaged in 6+ months
Never purchase email lists — they contain spam traps that will destroy your reputation

Feedback Loops

Register for feedback loop (FBL) programs with major ISPs. These notify you when recipients mark your email as spam, allowing you to remove them from your list promptly.