This documentation explains the various types of delivery issues and how Acteol manages them to protect your brand.
Email provider differences
There are several email providers, and each one of them handle emails deliveries differently.
Gmail / Google workspace
There are billions of users worldwide.
Strict spam filtering, reputation-based delivery, requires proper authentication.
May delay first-time senders. Maintain bounce rate <0.3%.
Microsoft (Outlook/Office 365)
There are 400M+ users.
SmartScreen filtering, long-term reputation tracking, aggressive rate limiting.
Register with SNDS. Keep complaint rate <0.1%.
Yahoo / AOL
There are 225M+ users.
Domain-based reputation, strict volume limits, requires strong authentication.
Subscribe to feedback loop. Complaint rate <0.1%.
Apple iCloud Mail
There are 850M+ users.
Strong privacy focus, aggressive spam filtering, requires proper authentication (SPF/DKIM/DMARC). Limited sender feedback.
Prioritizes user privacy and experience.
Understanding email delivery outcomes
When an email is sent, one of three outcomes occurs: successful delivery, temporary failure (soft bounce), or permanent failure (hard bounce). Each requires different handling to maintain optimal deliverability rates and protect your sender reputation.
Soft Bounces : Temporary delivery issues
Soft bounces are temporary delivery failures that may resolve on their own. Think of them like a "busy signal" when calling someone: the recipient exists, but you can't reach them right now.
Type | Description | Common Causes | Frequency |
Mailbox full | Recipient's email storage is at capacity. | Exceeded quota, inactive account. | 2-5% |
Server issues | The receiving server is experiencing problems. | Maintenance, outages, overload. | 1-3% |
Greylisting | Anti-spam technique (temporary rejection) | Security measure, normal behaviour. | 10-20% |
Rate limiting | Too many emails are sent too quickly. | Sending volume exceeds limits. | 5-15% |
📌Note: Acteol automatically retries soft bounces with increasing delays: 15 min → 1 hour → 4 hours → 24 hours → 48 hours. After 5 consecutive failures, the address is temporarily suspended to protect sender reputation.
Hard bounces : Permanent delivery failures
Hard bounces are permanent failures - the email will never be delivered to this address. These addresses must be removed immediately from your mailing list.
What's an acceptable bounce rate?
High bounce rates signal to email providers that your list quality is poor, you may be sending spam, you're not properly maintaining your database, or your practices may not be legitimate. This results in lower inbox placement rates, possible blacklisting, reduced overall deliverability, and damaged brand reputation.
Type | Description | % of Hard Bounces |
Invalid address | Email address doesn't exist | 40-50% |
Domain not found | Domain doesn't exist or no MX records | 10-15% |
Account disabled | User account deactivated | 15-20% |
Spam/Blacklist | IP or domain blocked | 10-15% |
Policy violation | Message violates server policies | 5-10% |
Industry standards:
Hard bounces: Less than 2% is normal.
Soft bounces: Less than 3% is normal.
Combined: Keep total bounce rate under 5%
📌Note: Hard bounced addresses are immediately flagged, removed from all active lists, and added to a permanent suppression list. This protects your sender reputation and prevents blacklisting.
Campaign health monitoring
Below are the key metrics to track for every campaign:
Metric | 🟢 Excellent | 🟡 Warning | 🔴 Critical |
Delivery rate | 95-98% | 90-95% | <90% |
Hard bounce rate | <2% | 2-5% | >5% |
Soft bounce rate | <3% | 3-5% | >5% |
Complaint rate | <0.1% | 0.1-0.3% | >0.3% |
Spam folder rate | <5% | 5-10% | >10% |
📌Note: If you have noticed a high hard bounce rate (>5%) the immediate actions are:
Pause the campaign immediately.
Review recent data imports for invalid addresses.
Check email collection process for validation issues.
Analyse bounced addresses for patterns (common domains, typos).
Refer to Acteol's support team.