feat: add ability to disable POP3 and IMAP servers via null port configuration

[Copilot]

POP3 and IMAP servers now consume ports even when unused. Users need the ability to disable them independently.

Changes

• Pop3Server.cs: Early return in StartAsync() when Pop3Port is null (matching existing IMAP behavior). Fixed ListeningPorts to return empty array when disabled instead of defaulting to port 110.

• appsettings.json: Document that null port values disable servers.

• CommandLineParser.cs: Update help text to show empty string disables servers.

Usage

Command line:

smtp4dev --pop3port="" --imapport=""

Config file:

{
  "ServerOptions": {
    "Pop3Port": null,
    "ImapPort": null
  }
}

Environment variables:

export ServerOptions__Pop3Port=
export ServerOptions__ImapPort=

Disabled servers log: [INF] POP3 server disabled - no port configured

Default behavior unchanged - both servers remain enabled by default.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Ability to disable POP3</issue_title>
<issue_description>POP3 is new to v3.11.0. I'd ask for the ability to disable it, since if one uses IMAP, it's not always necessary but uses a port. Possibly, others would be interested in similarly disabling IMAP.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Ability to disable POP3 #1997

---

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[rnwood]

📊 Code Coverage Report

Coverage Type	Percentage	Status
Line Coverage	14.3%	🔴
Branch Coverage	4.9%	🔴
Method Coverage	17.6%	🔴

📁 Coverage by Namespace

Namespace	Line Coverage	Branch Coverage	Method Coverage	Classes
LumiSoft.Net	0% 🔴	0% 🔴	0% 🔴	23
LumiSoft.Net.AUTH	0% 🔴	0% 🔴	0% 🔴	18
LumiSoft.Net.IMAP	1.7% 🔴	0.4% 🔴	3.9% 🔴	122
LumiSoft.Net.IMAP.Client	0% 🔴	0% 🔴	0% 🔴	8
LumiSoft.Net.IMAP.Server	0% 🔴	0% 🔴	0% 🔴	25
LumiSoft.Net.IO	0% 🔴	0% 🔴	0% 🔴	13
LumiSoft.Net.Log	0% 🔴	0% 🔴	0% 🔴	3
LumiSoft.Net.Mail	0% 🔴	0% 🔴	0% 🔴	14
LumiSoft.Net.MIME	0% 🔴	0% 🔴	0% 🔴	41
LumiSoft.Net.TCP	0% 🔴	0% 🔴	0% 🔴	6
LumiSoft.Net.UDP	0% 🔴	0% 🔴	0% 🔴	3
Rnwood.Smtp4dev	1.9% 🔴	3.3% 🔴	12% 🔴	14
Rnwood.Smtp4dev.ApiModel	58.5% 🔴	54.5% 🔴	44.3% 🔴	17
Rnwood.Smtp4dev.Controllers	3.5% 🔴	4.7% 🔴	9.2% 🔴	11
Rnwood.Smtp4dev.Data	55.6% 🔴	40.9% 🔴	60% 🟡	3
Rnwood.Smtp4dev.DbModel	72.1% 🟡	0% 🔴	67.3% 🟡	6
Rnwood.Smtp4dev.DbModel.Projections	100% 🟢	0% 🔴	100% 🟢	1
Rnwood.Smtp4dev.Hubs	0% 🔴	0% 🔴	0% 🔴	1
Rnwood.Smtp4dev.Migrations	90.2% 🟢	0% 🔴	71.7% 🟡	23
Rnwood.Smtp4dev.Server	15.4% 🔴	14% 🔴	20.3% 🔴	15
Rnwood.Smtp4dev.Server.Imap	84.8% 🟢	85.3% 🟢	78.9% 🟡	2
Rnwood.Smtp4dev.Server.Pop3	76.1% 🟡	65.2% 🟡	96.8% 🟢	2
Rnwood.Smtp4dev.Server.Pop3.CommandHandlers	48.3% 🔴	26.1% 🔴	84.6% 🟢	12
Rnwood.Smtp4dev.Server.Settings	67.1% 🟡	16.7% 🔴	72.1% 🟡	10
Rnwood.Smtp4dev.Service	0% 🔴	0% 🔴	0% 🔴	5
Rnwood.Smtp4dev.TUI	0% 🔴	0% 🔴	0% 🔴	9
Rnwood.SmtpServer	72.1% 🟡	63.2% 🟡	68.3% 🟡	36
Rnwood.SmtpServer.Extensions	67.9% 🟡	25% 🔴	91.3% 🟢	6
Rnwood.SmtpServer.Extensions.Auth	59% 🔴	47.6% 🔴	57.5% 🔴	23
Rnwood.SmtpServer.Verbs	92.9% 🟢	92% 🟢	100% 🟢	12

Overall Coverage Details:

• Covered Lines: 5983 / 41714
• Covered Branches: 587 / 11973
• Covered Methods: 701 / 3973
• Assemblies Tested: 3
• Total Classes: 484

📈 View Full Coverage Report

Enhanced coverage report with namespace breakdown - Azure DevOps Build #3.12.0-ci20251228104_pr1998 20251228.5

[rnwood]

@copilot The build triggered by this PR has failed. Please use the Azure DevOps REST API to investigate and fix the issues.

🚨 IMPORTANT: Only proceed if this is the most recent commit on your branch. If a newer commit exists, ignore this notification.

Build Details:

• Build ID: 5450
• Build URL: https://dev.azure.com/rnwood/smtp4dev/_build/results?buildId=5450 (for reference)
• Commit: d899140
• Build Status: FAILED

Instructions for @copilot:

1. First verify this is the latest commit - If d899140 is not the most recent commit in this PR branch, ignore this notification

2. Use Azure DevOps REST API to get build details and failures:
   `�ash

   Get build overview

   curl -s "https://dev.azure.com/rnwood/smtp4dev/_apis/build/builds/-version=6.0" | jq '{status: .status, result: .result, sourceVersion: .sourceVersion}'

   Get failed tasks and their logs

   curl -s "https://dev.azure.com/rnwood/smtp4dev/_apis/build/builds/5450/timeline?api-version=6.0" | jq '.records[] | select(.result == "failed") | {name: .name, task: .task.name, errorCount: .errorCount, logId: .log.id}'

   Get specific error details from a failed task log (replace LOG_ID)

   curl -s "https://dev.azure.com/rnwood/smtp4dev/_apis/build/builds/5450/logs/LOG_ID" | grep -i "error|failed"
   `

3. Analyze the error messages from the API responses to identify compilation errors, test failures, or other issues

4. Make targeted fixes based on the specific error messages found

5. Build locally after making fixes to verify the solution

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