Troubleshooting Common Issues in MailBee.NET ObjectsMailBee.NET Objects is a powerful .NET library for handling email tasks such as sending, receiving, parsing, and processing messages. While it’s feature-rich and stable, developers can still encounter issues during integration or runtime. This article walks through common problems, diagnostic steps, and practical fixes to help you get MailBee.NET Objects working smoothly in your applications.
1. Installation and Licensing Problems
Common symptoms
- Library not found at compile time (missing assembly references).
- License exceptions or runtime errors indicating unregistered components.
Diagnostics and fixes
- Ensure you have the correct NuGet package installed (search for MailBee.NET Objects or the vendor’s package name). If using a downloaded DLL, add a reference to the correct assembly matching your target framework (e.g., .NET Framework vs .NET Core/.NET 5+).
- Confirm that the assembly version matches your code expectations. Remove older versions from the project references and the Global Assembly Cache (GAC) if necessary.
- For licensing issues, verify you have a valid license key and that it’s applied according to vendor instructions (often via a license file or registration call). If you’re switching between trial and licensed builds, fully remove trial artifacts and rebuild.
Example checks
- In Visual Studio, open References -> Manage NuGet Packages -> Installed, and confirm MailBee is listed.
- Inspect bin/debug (or publish) output to verify the MailBee DLL is copied.
2. SMTP Sending Failures
Common symptoms
- Exceptions like SmtpException, connection timeouts, authentication failures, or messages stuck in queue.
Diagnostics
- Verify SMTP server address, port, and SSL/TLS settings.
- Check credentials (username/password) and whether the server requires specific authentication methods (e.g., OAuth2).
- Look at inner exception details for socket errors or server responses.
- Confirm firewall or antivirus software isn’t blocking outbound SMTP connections.
- Test connectivity using telnet: telnet smtp.example.com 587 (or ⁄465).
Fixes
- Explicitly set MailBee SMTP client properties for port and ssl:
- Use port 587 with STARTTLS for many providers.
- Use port 465 for implicit SSL where required.
- Enable authentication and set credentials correctly.
- If using OAuth2, implement token acquisition and set the appropriate authentication mechanism supported by MailBee.
- For timeouts, increase the SMTP timeout setting.
- If behind a corporate proxy or firewall, coordinate with IT to allow SMTP traffic or use an API-based email provider (e.g., SendGrid) that supports HTTP(S).
Code example (conceptual)
var smtp = new Smtp(); smtp.Server = "smtp.example.com"; smtp.Port = 587; smtp.SslMode = SslMode.StartTls; smtp.UserName = "[email protected]"; smtp.Password = "password"; smtp.Connect(); smtp.Send(message); smtp.Disconnect(); 3. IMAP/POP3 Connection and Authentication Issues
Common symptoms
- Cannot connect to mail server, authentication failures, or inability to fetch folders/messages.
Diagnostics
- Verify IMAP/POP3 host, port, and SSL settings.
- Confirm that the account allows IMAP/POP access (some providers require enabling it in account settings).
- Check for multi-factor authentication (MFA) and provider-specific app passwords or OAuth2 requirements.
- Examine server responses and exceptions for protocol-specific errors.
Fixes
- Use correct ports:
- IMAP over SSL: 993
- IMAP without SSL (STARTTLS): 143
- POP3 over SSL: 995
- If provider uses OAuth2, integrate OAuth flow and supply access tokens to MailBee authentication methods.
- Enable “less secure apps” or generate an app-specific password if the provider requires it (e.g., legacy Google setups).
- Increase network timeouts if connections are slow.
4. Message Parsing and Encoding Problems
Common symptoms
- Garbled subject or body text (seen with non-ASCII characters), missing attachments, or incorrect content type handling.
Diagnostics
- Inspect raw MIME source to see Content-Type, charset, Content-Transfer-Encoding headers.
- Check whether attachments are present in the MIME but not shown in the UI.
- Determine whether messages are multipart/alternative, multipart/mixed, or nested multipart.
Fixes
- Ensure MailBee is configured to decode various encodings (quoted-printable, base64).
- Explicitly access message.TextBody, message.HtmlBody, or iterate MIME parts to locate content.
- For charset issues, convert to a known encoding (e.g., UTF-8) when displaying:
- Use message.GetTextBodyWithCharset(“utf-8”) or equivalent API to force proper decoding.
- Handle inline images and CID references by resolving Content-ID links to saved files and replacing src attributes.
Example: extracting attachments
foreach (var attach in message.Attachments) { var fileName = attach.FileName; attach.SaveToFile(Path.Combine(folder, fileName)); } 5. Performance and Memory Issues
Common symptoms
- High memory usage when processing many messages, slow folder listing, or long message parsing times.
Diagnostics
- Profile memory and CPU while processing to locate hotspots.
- Watch for loading entire mailboxes into memory instead of streaming.
- Check for repeated allocations or keeping large objects referenced (e.g., storing full Message objects in long-lived collections).
Fixes
- Use fetching strategies that download only headers first, then bodies on demand (IMAP FETCH BODY.PEEK[] or similar).
- Dispose or release Message objects when done. Use “using” patterns where applicable.
- Process messages in batches and avoid loading attachments unless needed.
- For large attachments, stream to file rather than loading into memory.
- Update MailBee to the latest version for performance fixes.
6. TLS/SSL and Certificate Errors
Common symptoms
- SSL/TLS handshake failures, certificate validation exceptions, or “remote certificate is invalid” errors.
Diagnostics
- Inspect inner exception for certificate details.
- Verify server certificate chain via openssl or browser.
- Confirm system clock is correct — expired or not-yet-valid certificates will fail.
Fixes
- Enable proper SSL/TLS mode in the client (SslMode.Ssl, SslMode.StartTls).
- If using self-signed certificates in development, add certificate to trusted store or implement a certificate validation callback to accept specific certs (use only in trusted environments).
- Update OS certificate store if necessary.
- Ensure TLS 1.⁄1.3 enabled in your .NET runtime (ServicePointManager.SecurityProtocol or runtime defaults).
7. Threading and Concurrency Issues
Common symptoms
- Race conditions, deadlocks, or exceptions when using MailBee from multiple threads.
Diagnostics
- Review code for shared MailBee client instances accessed concurrently.
- Check stack traces for synchronization-related exceptions.
Fixes
- Treat client objects (Smtp, Imap, Pop3) as non-thread-safe unless otherwise documented. Create separate instances per thread or use synchronization (locks).
- For high throughput, use a pool of client instances rather than sharing one.
- Avoid blocking UI threads; perform network operations on background threads or async patterns.
8. Handling Large Mailboxes and Folder Synchronization
Common symptoms
- Slow folder synchronization, missed new messages, or partial folder listings.
Diagnostics
- Check whether folder contains thousands of messages; observe server-side limits or rate limits.
- Verify whether the client uses UID-based synchronization or sequence numbers that change.
Fixes
- Use IMAP UID-based synchronization and STORE/UID commands to track changes.
- Use server-side search (UID SEARCH) to find recent messages instead of listing entire folders.
- Implement incremental sync using mod-sequences or IMAP IDLE where supported.
9. Attachment Corruption or Missing Inline Content
Common symptoms
- Attachments that fail to open, incorrect file sizes, or inline images not displayed in email HTML.
Diagnostics
- Compare saved attachment bytes against original MIME parts.
- Verify Content-Transfer-Encoding and decoding steps.
Fixes
- Ensure attachments are saved with correct binary mode and encoding is decoded (base64 → bytes).
- For inline images, ensure Content-ID references match attachment Content-ID headers. Extract inline parts and save with their original filenames and proper content-type.
10. Logging and Diagnostic Best Practices
What to log
- Connection attempts (host, port, SSL mode).
- Server responses and error codes (avoid logging secrets like passwords or full message bodies in production).
- Timestamps and durations for key operations (connect, fetch, send).
How to enable detailed logs
- Use MailBee’s built-in logging facilities if available, or wrap calls with try/catch to capture exceptions and server replies.
- In development, log raw SMTP/IMAP sessions to diagnose protocol-level issues.
Quick Troubleshooting Checklist
- Verify addresses, ports, and SSL/TLS mode.
- Confirm credentials and authentication method (password vs OAuth2).
- Inspect raw MIME for parsing and encoding issues.
- Use header-only fetches and stream attachments for performance.
- Keep client instances single-threaded or synchronized.
- Update to latest MailBee and .NET runtime for bug and security fixes.
If you want, I can convert this into a troubleshooting flowchart, provide code samples for OAuth2 with a specific provider, or help debug a concrete error message you’re seeing — paste the exception and relevant code.
Leave a Reply