Troubleshooting Common TOTO Mail Sender IssuesTOTO Mail Sender is a popular tool for sending transactional and marketing emails. Like any mail-sending system, it can run into problems that affect deliverability, authentication, performance, or configuration. This article walks through the most common issues users face with TOTO Mail Sender, explains likely causes, and provides step-by-step troubleshooting and fixes you can apply.
1. Messages Not Being Delivered (Bounces / Soft Bounces)
Symptoms:
- Messages appear to be sent but recipients never receive them.
- You see bounce notifications or a high soft-bounce rate.
Common causes:
- Invalid recipient addresses or outdated lists.
- Temporary recipient server issues or mailbox full (soft bounce).
- Sender IP/domain reputation problems or blacklisting.
- Rate limits imposed by recipient servers.
Troubleshooting steps:
- Check bounce logs in TOTO Mail Sender. Identify bounce types and codes (hard vs. soft).
- Validate recipient addresses before sending with a list-cleaning tool.
- Retry soft-bounced messages after a delay; remove hard-bounced addresses immediately.
- Inspect your sending patterns—reduce send rate and enable throttling if needed.
- Monitor IP/domain reputation and check public blacklists. If blacklisted, follow delisting procedures and review sending practices to prevent recurrence.
2. Emails Landing in Spam Folder
Symptoms:
- Emails reach recipients but consistently go to spam or junk.
Common causes:
- Missing or misconfigured authentication (SPF, DKIM, DMARC).
- Low sender reputation due to spam complaints or poor engagement.
- Spammy content, misleading subject lines, or heavy use of images/links.
- Lack of proper unsubscribe link or mailing-list management.
Troubleshooting steps:
- Verify SPF, DKIM, and DMARC records for your sending domain. Use online diagnostics to confirm they pass.
- Ensure the “From” and “Return-Path” domains are aligned and consistent with authentication.
- Review content: avoid spam-trigger words, balance text-to-image ratio, and include a clear unsubscribe link and physical address.
- Warm up new IPs gradually; maintain consistent sending volume.
- Ask engaged recipients to whitelist your sending address and use re-engagement campaigns to remove unresponsive users.
3. Authentication Failures (SPF / DKIM / DMARC Issues)
Symptoms:
- Diagnostic tools or recipient servers report authentication failures.
- DMARC reports show failures or high “none/quarantine” actions.
Common causes:
- DNS records missing, incorrect, or not propagated.
- DKIM selector mismatch or private/public key misconfiguration.
- Forwarding services that rewrite headers and break DKIM.
Troubleshooting steps:
- Check DNS propagation for SPF, DKIM, and DMARC records. Use a DNS lookup tool to confirm the correct entries are visible.
- Confirm DKIM selector and public key match what TOTO Mail Sender expects. Recreate keys if needed.
- Ensure SPF includes TOTO Mail Sender’s sending IPs/domains (add include mechanisms or IP ranges).
- If forwarding is common for your recipients, consider using DMARC policy monitoring before enforcement and implement ARC (Authenticated Received Chain) if supported.
- Review DMARC aggregate and forensic reports to identify sources of failure.
4. High Complaint Rates / Spam Reports
Symptoms:
- Elevated user spam complaints and abuse reports.
- ISPs throttle or block your traffic.
Common causes:
- Sending to recipients who didn’t opt in.
- Misleading subject lines or frequent unsolicited sends.
- Poor list hygiene including stale or purchased lists.
Troubleshooting steps:
- Stop sending to questionable lists immediately. Adopt confirmed opt-in (double opt-in) for new subscribers.
- Add visible unsubscribe links and honor unsubscribe requests promptly.
- Segment lists by engagement and reduce frequency for less-active users. Remove consistently inactive addresses.
- Review send cadence, content relevance, and target audience to reduce complaints.
- Monitor complaint rates through TOTO Mail Sender dashboards and ISP feedback loops. If an ISP provides FBL data, follow their remediation steps.
5. Throttling or Temporary Blocks by Recipient Servers
Symptoms:
- Recipients’ servers temporarily reject or postpone delivery with 4xx SMTP codes.
- Sudden slowdowns in delivery throughput.
Common causes:
- Sending bursts too quickly to a single domain or ISP.
- ISP rate-limiting to protect recipients from spam.
Troubleshooting steps:
- Implement per-domain throttling in TOTO Mail Sender or your sending pipeline.
- Spread sends over time and stagger batches to major ISPs (e.g., Gmail, Yahoo).
- Monitor and respect bounce/backoff signals from recipient servers. Implement exponential backoff for retries.
- Use dedicated sending IP addresses if you have high volume and need consistent throughput; warm them up properly.
6. Template Rendering Problems (HTML/CSS Issues)
Symptoms:
- Recipients report broken layout, missing images, or incorrect formatting.
- Rendering differs across email clients (Gmail, Outlook, mobile apps).
Common causes:
- Client-specific CSS handling and HTML support differences.
- External images blocked by the client or broken image URLs.
- Use of unsupported HTML/CSS features (floats, web fonts, complex scripts).
Troubleshooting steps:
- Test templates in major clients and devices using an email-preview/testing service.
- Use inline CSS and table-based layouts for maximum compatibility, and avoid advanced CSS.
- Host images on secure (HTTPS) servers and verify URLs. Include proper Content-ID for embedded images if used.
- Provide a well-styled plain-text version of every email for clients that block HTML.
7. API or SMTP Connection Errors
Symptoms:
- Integration errors when TOTO Mail Sender’s API or SMTP connection fails.
- Timeout, authentication, or malformed request errors.
Common causes:
- Incorrect API keys, credentials, or endpoint URLs.
- Firewall or network blocking outbound connections.
- Rate limits or quota exceedance on the account.
Troubleshooting steps:
- Confirm API keys/SMTP credentials are correct and active. Rotate keys if compromised.
- Check network/firewall settings to allow outbound connections to TOTO Mail Sender endpoints and ports (typically 587 for SMTP-TLS).
- Inspect logs for HTTP status codes or SMTP reply codes; address authentication (535), rate limit (429), or timeout issues.
- If hitting rate limits, implement client-side throttling and request higher quotas if necessary.
8. Tracking and Analytics Not Recording
Symptoms:
- Opens, clicks, or other engagement metrics are lower than expected or missing entirely.
Common causes:
- Image-based open tracking blocked by clients, or recipients viewing plain-text emails.
- Link-wrapping/tracking disabled or misconfigured.
- DNS or redirect issues breaking tracking domains.
Troubleshooting steps:
- Verify tracking is enabled in campaign settings and that tracking domains are configured correctly.
- Ensure your tracking domain uses HTTPS and has proper DNS records (CNAME) pointing to TOTO Mail Sender if required.
- Remind that open rates are inherently imperfect—lean on click and conversion metrics.
- Test links to confirm tracking redirects route to the intended final URL.
9. Attachments Not Delivered or Stripped
Symptoms:
- Recipients report missing attachments or attachments removed by email clients.
Common causes:
- Attachment size limits exceeded.
- Attachment types blocked by recipient servers (executables, archives).
- Security filters stripping attachments or converting them to links.
Troubleshooting steps:
- Check attachment size limits for both TOTO Mail Sender and recipient domains; host large files externally and provide download links.
- Avoid sending prohibited or risky file types; compress files into accepted formats or provide secure download pages.
- If attachments are necessary, sign emails with DKIM and ensure SPF is correct to reduce server-side stripping.
10. Deliverability After Domain or IP Change
Symptoms:
- Sudden drop in deliverability after switching sending domain or IP address.
Common causes:
- New IP/domain has no sending history; poor reputation or no warming.
- Missing authentication or misaligned DNS for the new sending identity.
Troubleshooting steps:
- Warm up new IPs gradually: start with small, highly engaged segments and slowly increase volume over days/weeks.
- Ensure all authentication (SPF, DKIM, DMARC) is correctly set up for the new domain/IP before sending at scale.
- Monitor engagement and complaint metrics closely; pause and reassess if problems appear.
Best Practices to Prevent Issues
- Use double opt-in and maintain strict list hygiene.
- Set up and monitor SPF, DKIM, and DMARC from day one.
- Warm up new IPs and senders gradually.
- Segment users by engagement and tailor frequency/content.
- Keep templates simple and test across major clients.
- Monitor reputation, bounce rates, and ISP feedback loops continuously.
Quick Troubleshooting Checklist
- Check bounce and delivery logs in TOTO Mail Sender.
- Validate SPF/DKIM/DMARC DNS records and propagation.
- Cleanse recipient lists and remove hard bounces.
- Implement throttling and IP warm-up when needed.
- Test templates and tracking domains in multiple clients.
- Verify API/SMTP credentials and network connectivity.
If you want, I can tailor this article with screenshots, step-by-step commands for DNS setup, or a checklist specific to your TOTO Mail Sender account and DNS provider—tell me which details you want included.
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