Why It Matters
A low acceptance rate is an early warning sign. If mail servers are rejecting your messages before they even reach a spam filter, something's fundamentally wrong — bad authentication, a blocklisted IP, or a list full of invalid addresses. Most healthy senders sit above 95% acceptance. Dip below 90% and you've got a problem that needs immediate attention.
How It Works
When your sending server connects to the recipient's server via SMTP, the receiving server decides whether to accept or reject the message. Rejections come back as bounce codes — a 550 means the address doesn't exist, a 554 might mean you've been blocked. Your acceptance rate is simply: (emails accepted / emails sent) x 100.
Acceptance and deliverability aren't the same thing. A server can accept your email and still dump it in the spam folder. Think of acceptance rate as getting past the front door — you still need good content and reputation to reach the inbox.
Quick Tips
- Clean your list regularly — invalid addresses are the #1 cause of rejections.
- Set up SPF, DKIM, and DMARC before you send anything. Missing authentication is an instant red flag.
- Monitor your bounce codes. A spike in 550 errors means your list hygiene needs work; 421 errors suggest throttling.