iPhone, iPad, Mac: install the mail profile, then open Settings → General → VPN & Device Management (iOS) or System Settings → Privacy & Security → Profiles (macOS) to finish.
Thunderbird, Outlook, most Android apps: just add an account with your email address and password; the settings are detected automatically.
Manual settings:
| Username | your full email address |
| Incoming (IMAP) | mx.dekross.com, port 993, SSL/TLS |
| Outgoing (SMTP) | mx.dekross.com, port 465 SSL/TLS (or 587 STARTTLS) |