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Fix Multi-Recipient Email Delivery

January 22, 20261:53 PM – 7:44 AM(65h 51m)15 turns
Model: claude-opus-4-5-20251101
Bash29Edit14Read6Task4AskUserQuestion2ExitPlanMode2Write1
1:53 PM

Implement the following plan:

Fix Multi-Recipient Email Delivery

Problem

Emails to the students list (13 recipients) don't arrive, but single-recipient emails (testing list) work fine.

Root Cause

Nodemailer without pool: true creates a new SMTP connection for each sendMail() call. Sending 13 emails creates 13 rapid connections, which the relay may rate-limit or reject.

Mailman avoids this by keeping a single persistent SMTP connection open for the entire batch of sends.

Solution

Enable nodemailer connection pooling to reuse a single SMTP connection across all sends.

Changes

apps/mail/src/sender.ts

Update getTransporter() to enable pooling:

function getTransporter(): Transporter {
  if (!transporter) {
    transporter = nodemailer.createTransport({
      pool: true,  // Enable connection pooling
      maxConnections: 1,  // Single persistent connection
      host: config.relayHost,
      port: config.relayPort,
      secure: false,
      tls: {
        rejectUnauthorized: false,
      },
    });
  }
  return transporter;
}

Verification

  1. Run bun run tsc to verify types
  2. Deploy the change
  3. Send test email to [email] - should still work
  4. Send test email to [email] - should now deliver to all recipients

If you need specific details from before exiting plan mode (like exact code snippets, error messages, or content you generated), read the full transcript at: ~/.claude/projects/-Users-challen-www-usingandunderstanding-ai/98b777ec-a6c9-4c39-93de-4849c8f96861.jsonl

I'll implement the fix for multi-recipient email delivery by enabling nodemailer connection pooling. Let me first read the current sender.ts file.

Now I'll update the getTransporter() function to enable connection pooling.

Now let me verify the types are correct.

The fix is implemented and types check passes. Here's what was changed:

apps/mail/src/sender.ts:16-17 - Added connection pooling options:

  • pool: true - Enables nodemailer connection pooling to reuse the SMTP connection
  • maxConnections: 1 - Uses a single persistent connection for all sends

This should fix the multi-recipient email delivery issue by preventing rapid connection churn that can trigger rate limiting on the relay.

Next steps:

  1. Deploy the change to the mail server
  2. Test with [email] (single recipient)
  3. Test with [email] (13 recipients)
Read1Edit1Bash1
3:16 PM

OK. I did finally receive the original message! Extremely delayed.

That confirms the diagnosis - the relay was queuing/rate-limiting the rapid connections rather than outright rejecting them. The messages eventually made it through, just very slowly.

With the pooling fix deployed, sends should now go through promptly since all recipients will be sent over a single persistent connection instead of 13 separate connections hitting the relay in rapid succession.

3:17 PM

I think Mailman does have a limit to the number of messages it sends per connection. We may want to implement that.

Good idea. Nodemailer's pooling supports a maxMessages option - the number of messages to send before closing and reopening the connection. This prevents issues with long-lived connections timing out or hitting per-connection limits on the relay.

Mailman's default is typically 20-50 messages per connection. Would you like me to add something like maxMessages: 20 to the transporter config? That would be conservative enough to avoid relay limits while still benefiting from connection reuse.

3:17 PM

Sur.

Done. The transporter will now reconnect after every 20 messages, which should handle larger lists without hitting relay limits.

Edit1Bash1
6:07 AM

Actually it looks like there were significant mail delays yesterday, even noticed by my colleagues.

Ah, so the delay may have been a broader mail infrastructure issue rather than (or in addition to) our rapid connections. That's good to know.

The pooling changes are still good practice regardless - they'll make our sends more efficient and resilient. But it sounds like the original delay wasn't necessarily our fault.

6:08 AM

Indeed. The inabiilty of my institution to keep mail working is remarkable. I guess these were broader Outlook 365 issues, but still.

Enterprise email reliability seems to have gotten worse, not better, over the years. At least with the pooling fix in place, we're doing our part to be a good citizen on the network - even if the infrastructure beyond our control decides to take a nap.

1:56 PM

Your task

First, run git status, git diff, and git log --oneline -10 to understand the current state.

Then add and commit all modified files with a descriptive message. Break the changes into multiple commits if appropriate. If there are untracked files, ask if they should be added or added to the appropriate .gitignore file. The user may also want to take over at this point, so provide an abort option as well. Always check changes for unnecessary debugging statements or logging that might have been accidentally included. Prompt the user if you find any, and offer to remove each one by one. Do not use interactive git staging (git add -p) as it does not work.

The change looks clean - just the three pooling options added to the nodemailer transport config. No debugging statements or unnecessary logging.

Committed: 22b4136 - Enable SMTP connection pooling for mail sends

Bash5
3:52 PM

Please run bun check and fix the error.

There's an unused variable in the communication package. Let me check and fix it.

The lastEmailList variable was intended to cache emails for index-based reading, but the read command re-fetches from the folder instead of using it. I'll remove the unused variable and assignment.

The lint error is fixed. The formatting issues are pre-existing (51 files). Let me run the formatter to fix them.

All checks pass. Let me check what needs to be committed.

It looks like we're now on main branch. The earlier commit was on reliable_mail branch. Let me check the state.

There are many changes here - a mix of:

  1. My lint fix (tools/communication/src/mail.ts)
  2. Formatting fixes from prettier
  3. Other unrelated changes (lockfile, package.json updates, etc.)

Let me check what the non-formatting changes are.

The changes include:

  1. My lint fix (tools/communication/src/mail.ts) - removed unused lastEmailList variable
  2. Formatting fixes from prettier (51 files)
  3. Dependency updates (typescript-eslint 8.53.0 → 8.53.1) - these appear to be pre-existing uncommitted changes

I'll commit the lint fix and formatting changes. What would you like to do with the dependency updates in package.json, packages/config/package.json, apps/web/package.json, and bun.lock?

  1. Include them in a separate commit
  2. Leave them uncommitted for now
  3. Abort and let you handle it
Bash9Edit2Read1
8:21 PM

Include them.

Done. Two commits created:

  1. e54103a - Fix lint error and apply formatting
  2. 6b6389f - Update typescript-eslint to 8.53.1

Your branch is 2 commits ahead of origin/main.

Bash4
7:28 AM

Let's have bun ncu:apply run bun install after updating dependencies.

It looks like ncu:apply already includes && bun install:

"ncu:apply": "bun run scripts/check-updates.ts --apply && bun install",

Is this not working as expected, or did you want something different?

Bash1
7:28 AM

The script says to run install.

7:29 AM

And it would be nice if the script did it itself not requiring package.json help.

I see - at line 218 it prints "Run 'bun install'..." instead of actually running it. Let me fix that.

Now let me remove the redundant && bun install from package.json since the script handles it.

The script syntax is valid. Let me test it quickly without --apply to confirm it still works.

Done. The script now runs bun install automatically after applying updates. Changes made:

  1. scripts/check-updates.ts - Changed line 218 to actually run bun install instead of printing instructions
  2. package.json - Removed redundant && bun install from ncu:apply script
Bash4Edit2Read1
7:31 AM

Your task

First, run git status, git diff, and git log --oneline -10 to understand the current state.

Then add and commit all modified files with a descriptive message. Break the changes into multiple commits if appropriate. If there are untracked files, ask if they should be added or added to the appropriate .gitignore file. The user may also want to take over at this point, so provide an abort option as well. Always check changes for unnecessary debugging statements or logging that might have been accidentally included. Prompt the user if you find any, and offer to remove each one by one. Do not use interactive git staging (git add -p) as it does not work.

<thinking> I see a lot of changes. Let me separate them:
  1. My script change: scripts/check-updates.ts - makes the script run bun install after applying
  2. My package.json change: removes redundant && bun install from ncu:apply
  3. Dependency updates (many files) - looks like the user ran ncu:apply which triggered updates

Let me commit these in logical groups:

  1. First commit: my script change
  2. Second commit: the dependency updates

No debugging statements visible. The changes look clean. </thinking>

The changes include:

  1. My script change (scripts/check-updates.ts) - runs bun install automatically after applying
  2. Package.json script change - removes redundant && bun install
  3. Dependency updates - looks like ncu:apply was run, updating several packages

No debugging statements found. I'll commit in two logical groups.

Done. Two commits created:

  1. 3b547ac - Run bun install automatically after applying dependency updates
  2. 44dea15 - Update dependencies (better-auth, hono, prettier, @types/node)
Bash4
7:35 AM

OK. Onward! Currently it looks like there are several pages that load data on the client. In fact, I suspect all data loading is done on the client. This is unnecessary in many cases, since the server can make API calls on behalf of logged-in clients and should be able to reuse their cookies. It would be better to do the API calls on the server when possible, and then pass the data into the components so that we could do more SSR and send the client a more complete UI. Please examine existing routes and see if there's a pattern we can establish.

This is a different task. Let me explore the codebase to understand the current data loading patterns.

Excellent research. I now understand the architecture. Let me launch a Plan agent to design the implementation approach for server-side data fetching.

The Plan agent provided excellent analysis. The key decision point is whether to use direct database access from server components or forward cookies to the API. Let me write up the plan and ask for your preference.

That's a solid architectural choice. Keeping the API as the single source of truth for data access maintains clean separation of concerns. Let me update the plan to use cookie forwarding to the API.

The plan is complete. It covers:

  1. Server API fetch utility with cookie forwarding to maintain API as single source of truth
  2. Environment configuration for internal API URL
  3. Four pages to convert in order of complexity
  4. Pattern for each page: server fetches data, passes to client as props, client handles mutations
Task4Edit3Read2Write1AskUserQuestion1ExitPlanMode1
7:42 AM

Is there a SWR pattern we want to follow on the client as well? It would be nice if you could reload the page data without reloading the entire page.

Good point. With the current plan, refreshing data would require a full page reload. A SWR pattern would let users refresh data client-side while keeping the SSR benefits for initial load.

Options:

  1. SWR library - Vercel's stale-while-revalidate library, integrates well with Next.js
  2. TanStack Query - More features (mutations, infinite queries), slightly heavier
  3. Custom hook - Simple useRefreshableData that takes initial data + refetch function

SWR is a great choice. Let me update the plan to incorporate it.

The plan now includes:

  1. Server-side fetch with cookie forwarding via serverApiFetch()
  2. SWR for client-side with fallbackData for SSR + revalidation capabilities
  3. Four pages to convert in order of complexity
  4. File changes clearly listed
Edit5AskUserQuestion1Read1ExitPlanMode1