Two Powerful Blocking Systems

CodaMail provides two distinct but complementary blocking systems that work at the SMTP protocol level. This means blocked mail is rejected during the connection handshake with a "User Unknown" error, rather than simply being hidden from view. This approach has significant benefits:

• Effective Spam Prevention: Senders receive a "bounce" notification, encouraging them to remove your address from their lists
• Reduced Server Load: Rejected mail is never processed or stored on our systems
• Complete Privacy Control: You determine exactly which addresses can receive mail and which senders can contact you

Let's examine how each system works and how to use them effectively.

System 1: Managing Catch-all Settings (Controlling Recipient Addresses)

The first blocking system controls which email addresses can receive mail. This is essential for managing your catch-all functionality, allowing you to enable or disable specific email addresses associated with your account.

How It Works

CodaMail allows you to have unlimited email addresses through account aliases and masked aliases. The Manage Catch-alls feature lets you control which of these addresses should actually receive mail.

You'll find this under Settings → Manage Catch-alls.

Two Operating Modes

The system has a master switch at the top that determines how it operates:

• Switch OFF (Default - Blacklist Mode): Any addresses you enter in the list are REJECTED. All other addresses deliver normally. This allows you to keep using all your catch-all features while blocking specific addresses that receive spam.
• Switch ON (Whitelist Mode): ONLY the addresses you list are accepted. All other addresses are rejected. This is much more restrictive, turning your catch-all into a whitelist, where you explicitly define which addresses can receive mail.

WARNING: If you turn the switch ON (whitelist mode) but don't add any addresses to your list, you will block ALL incoming mail, including mail to your primary address and helpdesk communications!

Entry Format Options

You can add entries in two formats:

• Just the alias part: For example, entering newsletter would affect newsletter@anydomain.com across all your enabled domains
• Full email address: For example, entering newsletter@specific-domain.com would only affect that specific address

This flexibility lets you block (or allow) categories of addresses across all domains or target specific address/domain combinations.

System 2: Block List (Controlling Sender Addresses)

The second blocking system controls which senders can send mail to you, regardless of which of your addresses they're trying to contact.

How It Works

When viewing a message, you can click the Block icon (skull and crossbones) at the top of the message view. This gives you options to block at different levels:

• Block just the email address - Only blocks mail from that specific sender address
• Block everything from subdomain.domain.tld - Blocks all mail from the specific domain and subdomain
• Block everything from domain.tld - Blocks all mail from that domain and all of its subdomains
• Block everything from TLD - Blocks any mail from any domain using that top-level domain (like .xyz, .info, etc.)

You can also manage your block list directly by going to Settings → Block List, where you can view your current blocks and add new ones manually.

Entry Format

You can add entries in three formats:

• Email address: e.g., spammer@example.com - Blocks a specific sender
• Domain: e.g., example.com - Blocks all senders from that domain
• Top-level domain: e.g., xyz - Blocks all senders from any domain ending in .xyz

TLD blocking is particularly powerful for blocking entire countries or categories of domains that are frequently sources of spam.

Note: When blocking a TLD, do not include the dot (e.g., use info not .info).

Comparing the Two Systems

Recommended Strategies

For Account Organization

Use the Catch-all Settings in the default mode (switch OFF) to disable specific addresses that start receiving spam. This allows you to continue using our powerful catch-all features while blocking problematic addresses.

For Spam Prevention

Use the Block List feature to aggressively block domains and TLDs that are frequent spam sources. This can dramatically reduce spam volume while maintaining your ability to use many different email addresses.

For Maximum Privacy

Combine both systems: use masked aliases for different purposes, and if one starts receiving unwanted mail, block the specific senders with the Block List. If an alias becomes completely compromised, disable it through the Catch-all Settings.

Protocol-Level Blocking

What makes CodaMail's blocking approach unique is that both systems operate at the SMTP protocol level, not just in your inbox. When a blocked sender attempts to contact you or when someone tries to email a disabled address, our server responds with a "User Unknown" error during the connection handshake.

This has several advantages over simply filtering messages:

• Senders receive immediate feedback that the address is invalid, encouraging them to remove it from their lists
• Blocked messages never enter our system, reducing server load and storage usage
• No trace of blocked messages appears in your account, keeping your inbox clean
• More effective at stopping persistent spam because it breaks the sender's delivery feedback loop

This protocol-level approach reflects our commitment to giving you complete control over your email experience, not just hiding unwanted messages from view.