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Mail & DNSUpdated: 02/11/2026

Netcup mail setup: SMTP, IMAP and deliverability

From a mailbox in web hosting to your own mail server: this guide shows the order, common ports and DNS checks for reliable delivery.

1. Mailbox and access

Create a mailbox in the Web Hosting Control Panel (WCP). The username is usually the full email address; set the password in the WCP. For external clients, take the hostname, port and SSL mode from the official guide.

  • Create the mailbox in the WCP and set a password.
  • Take hostname/ports from the official external mail client guide.
  • Test webmail first, then configure the desktop client.

2. Configure SMTP/IMAP

Common values are IMAP 993 with SSL/TLS and SMTP 465 with SSL/TLS or 587 with STARTTLS. The authoritative values are in the WCP and the official guide; do not copy them from old blog posts.

# Test IMAP (port 993)
openssl s_client -connect mail.example.com:993 -servername mail.example.com

# Test SMTP (port 465)
openssl s_client -connect mail.example.com:465 -servername mail.example.com

Note: Replace mail.example.com with the hostname from the WCP. A certificate error usually means the wrong hostname or port.

3. Port 25, rDNS and DNS authentication

For your own mail server, remove the SCP rule "netcup Mail block" and set a PTR/rDNS record that matches the HELO hostname. Then publish SPF, DKIM and DMARC.

# DNS checks
dig +short MX example.com
dig +short TXT example.com
dig +short TXT _dmarc.example.com
dig +short -x 203.0.113.10

Note: Without PTR and clean DNS authentication, large providers will spam-filter or reject your mail. An open port alone is not enough.

4. Test and debug

Test receiving in webmail first, then send to an external mailbox. On errors, check headers, WCP logs and DNS records. For migrations, use IMAP sync, not just a DNS switch.

Official sources

Email in web hostingMailboxes, aliases and forwarding.External mail clientsHostnames and ports.WebmailWebmail access.Spam filterFilter rules in the WCP.

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Frequently asked questions

Which SMTP and IMAP ports are correct?

The authoritative values are in the WCP and the official external mail client guide. Common values are IMAP 993 with SSL/TLS and SMTP 465 with SSL/TLS or 587 with STARTTLS.

Source
Why is port 25 blocked?

Netcup protects IP reputation and blocks outbound port 25 through the SCP rule "netcup Mail block". For your own mail server, remove the rule and configure rDNS/PTR plus SPF/DKIM/DMARC.

Source
Can I migrate mailboxes from web hosting to a VPS?

Yes, but not by a pure DNS switch. Use IMAP sync or a mail client to copy the mailboxes, and switch MX/SPF/DKIM/DMARC only afterwards.

Source