Understanding Email Bounce Types
Hard bounces and soft bounces behave very differently. Learn the SMTP codes behind each type and how AcelleMail handles them to protect your sender reputation.
Email Throttling and Rate Limits Explained
Why Throttling Matters
Sending too fast triggers spam filters and can get your account suspended. Every receiving mail server — and every sending service — enforces rate limits. Throttling tells AcelleMail to spread your campaign sends over time.
Common Provider Limits
| Provider | Default Limit | Notes |
|---|---|---|
| Amazon SES (sandbox) | 1 msg/sec, 200/day | Request production increase |
| Amazon SES (production) | 14 msgs/sec | Varies by account age |
| SendGrid Free | 100/day | Upgrade for more |
| SendGrid Essentials | 100 msgs/sec | |
| Mailgun Flex | 5,000/month free | |
| Gmail SMTP | 500/day | Not for bulk use |
| Your own Postfix | Unlimited* | Throttle by recipient ISP |
*Sending unlimited via your own server is technically possible but ISPs will throttle or reject bursts — configure wisely.
Configuring Throttling in AcelleMail
Navigate to Settings → Sending Servers → [your server] and set:
- Speed (emails/hour) — total throughput cap
- Sending limit — optional daily cap
For campaigns, you can also set per-campaign throttling under the Schedule tab.
Per-ISP Throttling Tips
Gmail, Yahoo, and Outlook each have informal limits for new IPs:
- Start with 200–500/day per ISP on a new IP.
- Ramp up 20–50% per week during warmup.
- Watch your Defer rate — a high defer count means you are sending too fast.
Use AcelleMail's Sending Server Pool to distribute load across multiple servers when a single server's limit is not enough.
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