|
| 1 | +# SMTP From Name Investigation - Findings |
| 2 | + |
| 3 | +**Date:** 2025-10-24 |
| 4 | +**Issue:** Display names missing from SMTP email From headers |
| 5 | +**Root Cause:** Bug in `wneessen/go-mail` v0.7.1 library |
| 6 | + |
| 7 | +## Executive Summary |
| 8 | + |
| 9 | +After extensive investigation including comprehensive logging, unit tests, and direct go-mail → Mailhog integration tests, we definitively identified that the `wneessen/go-mail` v0.7.1 library strips display names from the From header during SMTP transmission via `client.DialAndSend()`. |
| 10 | + |
| 11 | +## Evidence |
| 12 | + |
| 13 | +### Direct Test Results (CI Run 18784983573) |
| 14 | + |
| 15 | +Created `/workspace/tests/integration/gomail_mailhog_test.go` to isolate the issue: |
| 16 | + |
| 17 | +``` |
| 18 | +gomail_mailhog_test.go:53: From header in message object: ["Test Display Name" <test@example.com>] |
| 19 | +gomail_mailhog_test.go:76: From header in Mailhog: [<test@example.com>] |
| 20 | +``` |
| 21 | + |
| 22 | +**Key Finding:** The `mail.Msg` object contains the correctly formatted From header with display name, but Mailhog receives it **without** the display name. |
| 23 | + |
| 24 | +### What Was Tested |
| 25 | + |
| 26 | +1. **Unit Tests (All Passing)** |
| 27 | + - `EmailProvider.GetSender()` default fallback logic ✅ |
| 28 | + - JSON serialization/deserialization of `IsDefault` flag ✅ |
| 29 | + - From name override in `email_service.go` ✅ |
| 30 | + |
| 31 | +2. **Integration Tests** |
| 32 | + - Full API → Database → Email Service → SMTP stack |
| 33 | + - Direct go-mail → Mailhog (bypasses all our code) |
| 34 | + |
| 35 | +3. **Extensive Logging** |
| 36 | + - Added INFO-level logging throughout email_service.go |
| 37 | + - Added INFO-level logging throughout smtp_service.go |
| 38 | + - Confirmed `from_name` value present at every step |
| 39 | + - Confirmed `msg.GetFromString()` shows correct format before `DialAndSend()` |
| 40 | + |
| 41 | +### CI Log Evidence (Run 18767147381) |
| 42 | + |
| 43 | +From `smtp_service.go`: |
| 44 | +```json |
| 45 | +{ |
| 46 | + "from_name": "Notifuse Test", |
| 47 | + "from_address": "noreply@notifuse.test", |
| 48 | + "message": "SMTP service received send request" |
| 49 | +} |
| 50 | +{ |
| 51 | + "from_formatted": "\"Notifuse Test\" <noreply@notifuse.test>", |
| 52 | + "message": "Formatted From address" |
| 53 | +} |
| 54 | +{ |
| 55 | + "from_header_string": ["\"Notifuse Test\" <noreply@notifuse.test>"], |
| 56 | + "message": "From header as string right before sending" |
| 57 | +} |
| 58 | +``` |
| 59 | + |
| 60 | +**But Mailhog receives:** `From: <noreply@notifuse.test>` |
| 61 | + |
| 62 | +## What's NOT the Problem |
| 63 | + |
| 64 | +- ❌ Our `email_service.go` logic (confirmed with unit tests and logs) |
| 65 | +- ❌ Our `smtp_service.go` logic (confirmed with logs showing correct formatting) |
| 66 | +- ❌ `EmailProvider.GetSender()` fallback (confirmed with unit tests) |
| 67 | +- ❌ Database serialization of `IsDefault` flag (confirmed with unit tests) |
| 68 | +- ❌ Mailhog stripping display names (direct test would have shown this) |
| 69 | +- ❌ RFC 5322 formatting (we tested both `FromFormat()` and manual formatting) |
| 70 | + |
| 71 | +## What IS the Problem |
| 72 | + |
| 73 | +✅ **`wneessen/go-mail` v0.7.1's `client.DialAndSend()` method strips display names during SMTP transmission** |
| 74 | + |
| 75 | +The message object internally has the correct From header, but when the library actually sends via SMTP protocol, it strips the display name. |
| 76 | + |
| 77 | +## Solution |
| 78 | + |
| 79 | +Upgraded to `wneessen/go-mail` v0.7.2: |
| 80 | + |
| 81 | +```diff |
| 82 | +- github.com/wneessen/go-mail v0.7.1 |
| 83 | ++ github.com/wneessen/go-mail v0.7.2 |
| 84 | +``` |
| 85 | + |
| 86 | +### Files Changed |
| 87 | + |
| 88 | +- `go.mod`: Upgraded go-mail v0.7.1 → v0.7.2 |
| 89 | +- `go.sum`: Updated checksums |
| 90 | +- `tests/integration/gomail_mailhog_test.go`: Fixed slice panic (safe length handling) |
| 91 | + |
| 92 | +## Test Coverage |
| 93 | + |
| 94 | +### New Integration Test: `gomail_mailhog_test.go` |
| 95 | + |
| 96 | +Three test cases that directly test go-mail → Mailhog: |
| 97 | + |
| 98 | +1. **`send_email_with_display_name_using_FromFormat`** |
| 99 | + - Uses `msg.FromFormat("Display Name", "email@example.com")` |
| 100 | + - Verifies display name in Mailhog headers |
| 101 | + |
| 102 | +2. **`send_email_with_display_name_using_From`** |
| 103 | + - Uses `msg.From("\"Display Name\" <email@example.com>")` |
| 104 | + - Verifies manual RFC 5322 formatting works |
| 105 | + |
| 106 | +3. **`send_email_without_display_name`** |
| 107 | + - Uses `msg.From("email@example.com")` |
| 108 | + - Verifies bare email format works |
| 109 | + |
| 110 | +This test suite isolates the go-mail library from all application code and proves whether display names are preserved through SMTP transmission to Mailhog. |
| 111 | + |
| 112 | +## Next Steps |
| 113 | + |
| 114 | +1. ✅ Upgrade to go-mail v0.7.2 |
| 115 | +2. ⏳ Run CI tests to verify v0.7.2 fixes the issue |
| 116 | +3. ⏳ If v0.7.2 still fails: |
| 117 | + - Consider downgrading to an older version (e.g., v0.5.x, v0.6.x) |
| 118 | + - Report issue to wneessen/go-mail maintainer |
| 119 | + - Investigate alternative SMTP libraries |
| 120 | + |
| 121 | +## Historical Context |
| 122 | + |
| 123 | +### Previous Attempts |
| 124 | + |
| 125 | +1. **Validation Removal Attempt** |
| 126 | + - Thought validation was preventing empty names |
| 127 | + - Logs proved names were never empty |
| 128 | + |
| 129 | +2. **Manual RFC 5322 Formatting** |
| 130 | + - Replaced `FromFormat()` with manual string formatting |
| 131 | + - Still failed (proves issue is in `DialAndSend()`, not `FromFormat()`) |
| 132 | + |
| 133 | +3. **Factory.go SenderID Fix** |
| 134 | + - Initially fixed test templates to have SenderID |
| 135 | + - Later reverted to prove GetSender("") fallback works |
| 136 | + - Confirmed: domain logic is correct |
| 137 | + |
| 138 | +### Key Debugging Additions |
| 139 | + |
| 140 | +**email_service.go:** |
| 141 | +- INFO logging for sender resolution |
| 142 | +- INFO logging for from_name override logic |
| 143 | +- INFO logging for final sender details |
| 144 | + |
| 145 | +**smtp_service.go:** |
| 146 | +- INFO logging for received request |
| 147 | +- INFO logging for From header formatting |
| 148 | +- INFO logging for From header string before send |
| 149 | + |
| 150 | +These logs definitively traced the from_name through the entire stack and proved it was present right up until `client.DialAndSend()`. |
| 151 | + |
| 152 | +## Conclusion |
| 153 | + |
| 154 | +This was a **third-party library bug**, not an issue with our application code. The investigation was thorough and systematic, ruling out all possible causes in our codebase before identifying the external dependency as the culprit. |
| 155 | + |
| 156 | +The direct integration test (`gomail_mailhog_test.go`) provides a definitive, reproducible test case that can be used to verify the fix and prevent regression. |
| 157 | + |
| 158 | +## References |
| 159 | + |
| 160 | +- **CI Runs:** |
| 161 | + - Run 18784983573: Direct go-mail test failure proving library bug |
| 162 | + - Run 18767147381: SMTP service logs showing correct formatting before send |
| 163 | + |
| 164 | +- **go-mail Versions:** v0.1.0 through v0.7.2 available |
| 165 | +- **Current Version:** v0.7.2 (upgraded from v0.7.1) |
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