Fix Stalwart mail server compatibility for IMAP, CalDAV, and CardDAV

[Copilot]

Stalwart mail server fails with authentication errors on IMAP and returns 500 errors on CalDAV/CardDAV endpoints due to protocol implementation differences.

Changes

• IMAP authentication: Check LOGINDISABLED capability and use SASL PLAIN authentication when LOGIN command is unavailable

  caps := c.Caps()
  if caps != nil && caps.Has(imap.CapLoginDisabled) {
      auth := sasl.NewPlainClient("", username, password)
      if err := c.Authenticate(auth); err != nil {
          // handle error
      }
  } else {
      // use LOGIN command
  }

• CalDAV/CardDAV discovery: Add fallback to base URL path when WebDAV principal/home-set discovery fails

  calendars, err := c.FindCalendars(ctx, calendarHomeSet)
  if err != nil {
      // Fallback for servers with incomplete WebDAV discovery support
      calendars, err = c.FindCalendars(ctx, u.Path)
  }

All changes activate only when needed, maintaining compatibility with existing mail servers.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• git.sr.ht
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)
• https://api.github.com/repos/stalwartlabs/mail-server/issues
  • Triggering command: /usr/bin/curl curl -s REDACTED (http block)
• todo.sr.ht
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

add fixes for stalwart mailserver

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[Copilot]

Pull request overview

This PR adds compatibility fixes for Stalwart mail server by addressing authentication and service discovery issues across IMAP, CalDAV, and CardDAV protocols.

Changes:

• Add SASL PLAIN authentication fallback for IMAP when LOGIN command is disabled
• Add CalDAV calendar discovery fallback to base URL path when standard discovery fails
• Add CardDAV address book discovery fallback to base URL path when standard discovery fails

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
session.go	Adds capability check for LOGINDISABLED and uses SASL PLAIN authentication when LOGIN is unavailable
plugins/caldav/caldav.go	Adds fallback to base URL path when FindCalendars fails with calendar home set
plugins/carddav/plugin.go	Adds fallback to base URL path when FindAddressBooks fails with address book home set
.gitignore	Adds alps binary to ignored files

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.