Summary
- Registrar
- Alibaba Cloud Computing (Beijing) Co., Ltd.
- Status
- clientUpdateProhibited
- Created on
- February 25, 2014
- Expires on
- February 25, 2027
- Name servers
- ns5.nease.net, ns6.nease.net, ns8.nease.net, ns4.nease.net, ns2.nease.net, ns1.nease.net, ns3.nease.net
- Mail servers
- mx.ym.163.com
- DMARC
- Monitoring
- SPF
- Soft
- DKIM
- No key found among the common selectors
- Website
- See the website
Spoofing protection (DMARC)
E-mails spoofing this domain are only reported, not blocked.
DMARC tells mail servers what to do with an e-mail that claims to come from icourse163.org but fails SPF and DKIM checks.
- Policy
- Monitoring
- Subdomain policy
- Monitoring
- Messages covered
- 100%
- DKIM alignment
- Relaxed
- SPF alignment
- Relaxed
- Aggregate reports
- [email protected]
- Failure reports
- [email protected]
Record
v=DMARC1;p=none;fo=1;ruf=mailto:[email protected]; rua=mailto:[email protected]
Authorized senders (SPF)
E-mails sent by any other server are accepted but flagged as suspicious.
SPF lists the servers allowed to send e-mails for icourse163.org.
| Rule | Value | Result |
|---|---|---|
| include | spf.mail.163.com | Allowed |
| include | spf.163.com | Allowed |
| all | — | Suspicious |
Top-level DNS lookups: 2 of 10 allowed
Record
v=spf1 include:spf.mail.163.com include:spf.163.com ~all
MX, SPF, DKIM and DMARC: the e-mail records
Four DNS records make a domain's e-mail work. MX says where e-mails sent to icourse163.org arrive; SPF, DKIM and DMARC let mail servers check that an e-mail claiming to come from icourse163.org was really sent by this domain, which protects it against spoofing.
MX
An MX (Mail Exchanger) record designates a server that receives e-mails sent to the domain. When someone writes to an @icourse163.org address, their mail server queries the DNS for the domain's MX records, then delivers the message to the server they point to.
Example record
icourse163.org MX 10 mx1.icourse163.org. icourse163.org MX 20 mx2.icourse163.org.
What the record contains
- 10, 20
- Priority: the server with the lowest number is tried first. Servers with equal priority share the load.
- mx1.icourse163.org.
- Host name of the mail server. It must point to an A or AAAA record: an IP address or an alias (CNAME) is not allowed here.
- 0 .
- An MX "0 .", called a null MX, declares that the domain accepts no e-mail: sending servers give up at once instead of retrying.
Declaring at least two servers with different priorities avoids losing e-mails during an outage: sending servers retry for several days and fall back on the backup server. Without any MX, they try to deliver directly to the IP address of the domain.
SPF
SPF (Sender Policy Framework) is a TXT record listing the servers allowed to send e-mails on behalf of the domain. The receiving server checks that the sender is on this list. The final "all" rule says what to do with other servers: reject them (-all), flag their e-mails as suspicious (~all) or make no decision (?all).
Example record
icourse163.org TXT "v=spf1 mx include:_spf.google.com ip4:192.0.2.10 -all"
What the record contains
- v=spf1
- Identifies the record as an SPF policy. It must come first.
- ip4, ip6
- Allows a specific IP address or an address range, for example ip4:192.0.2.0/24.
- a, mx
- Allows the addresses of the domain itself (A record) or those of its mail servers (MX).
- include
- Allows the servers of another domain, usually a sending service: include:_spf.google.com for Google Workspace.
- -all, ~all
- Final rule, applied to every other server. Its qualifier decides what happens to them: - rejects them, ~ flags their e-mails as suspicious, ? makes no decision, + accepts them (avoid it).
A domain must publish only one SPF record, and its evaluation cannot exceed 10 DNS lookups (include, a, mx, exists, redirect). Beyond that, mail servers treat it as invalid.
DKIM
DKIM (DomainKeys Identified Mail) signs every outgoing e-mail with a private key. The matching public key is published in a TXT record at selector._domainkey.icourse163.org, so the recipient can check that the message really comes from the domain and was not altered on the way. The selector is chosen by each sending service and cannot be guessed: Dataweaz checks the most common ones (Google Workspace, Microsoft 365, Mailchimp, SendGrid…), so a key published under another selector may exist without appearing here.
Example record
google._domainkey.icourse163.org TXT "v=DKIM1; k=rsa; p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA…"
What the record contains
- v=DKIM1
- Protocol version. Optional but recommended, in which case it must come first.
- k
- Key algorithm: rsa, the most common, or ed25519.
- p
- Public key, base64-encoded. An empty value means the key has been revoked.
- t
- Flags: y marks a key in testing, whose failures must not be penalized; s forbids its use for subdomains.
Each sending service publishes its key under its own selector (google, selector1, k1…), which allows several keys and seamless rotation. A 2048-bit RSA key is recommended today.
DMARC
DMARC (Domain-based Message Authentication, Reporting and Conformance) builds on SPF and DKIM. Published on _dmarc.icourse163.org, it tells mail servers what to do with an e-mail that fails these checks (let it through, send it to spam or reject it) and where to send reports.
Example record
_dmarc.icourse163.org TXT "v=DMARC1; p=quarantine; rua=mailto:[email protected]; adkim=r; aspf=r"
What the record contains
- v=DMARC1
- Identifies the record as a DMARC policy. It must come first.
- p
- Policy applied to e-mails that fail the checks: none (monitoring only), quarantine (spam folder) or reject.
- sp
- Subdomain policy. Without it, subdomains follow the domain's policy.
- rua
- Address that receives daily aggregate reports about e-mails sent on behalf of the domain, whether they pass the checks or not.
- ruf
- Address that receives detailed failure reports, message by message. Few providers still send them.
- pct
- Percentage of e-mails subject to the policy, for a gradual rollout. 100 by default.
- adkim, aspf
- DKIM and SPF alignment: r (relaxed, a subdomain of the same domain is enough) or s (strict, the domain must be identical).
To roll out DMARC without blocking legitimate e-mails, start with p=none and an rua address, analyze the reports to find every service sending on behalf of the domain, then move to quarantine and finally to reject.
DNS records of icourse163.org
IP addresses (A and AAAA)
An A record maps the domain name to an IPv4 address: the address of the server that browsers contact to display the website. The AAAA record does the same for an IPv6 address. A domain can have several of them to spread visits across several servers.
| Type | IP address |
|---|---|
| A | 111.124.200.109 |
Name servers (NS)
NS records designate the authoritative DNS servers of the domain: they answer every question about its other records (A, MX, TXT…). They are provided by the registrar, the hosting provider or a dedicated DNS service, and several servers are declared so that the domain keeps working if one of them fails.
| Server | IP address |
|---|---|
| ns5.nease.net | 42.186.102.226 |
| ns6.nease.net | 54.228.156.72 |
| ns8.nease.net | 18.182.82.158 |
| ns4.nease.net | 8.147.116.45 |
| ns2.nease.net | 42.186.102.226 |
| ns1.nease.net | 42.186.168.126 |
| ns3.nease.net | 182.92.22.240 |
Mail servers (MX)
MX records point to the servers that receive e-mails sent to the domain, that is to @icourse163.org addresses. Each server has a priority: the one with the lowest number is tried first, the others take over if it fails. Without an MX record, the domain cannot receive e-mails.
| Priority | Server | IP address |
|---|---|---|
| 10 | mx.ym.163.com | 111.124.200.35 |
TXT records
TXT records hold free text. They are used to prove ownership of the domain to online services (Google, Microsoft, Facebook…) and to publish e-mail security rules: SPF on the domain itself, DMARC on _dmarc.icourse163.org.
| Name | Content |
|---|---|
| icourse163.org | v=spf1 include:spf.mail.163.com include:spf.163.com ~all |
| _dmarc.icourse163.org | v=DMARC1;p=none;fo=1;ruf=mailto:[email protected]; rua=mailto:[email protected] |
Related IP addresses
IPv4 addresses used by icourse163.org: website, name servers, mail servers and senders authorized by SPF.
| IP address | Used for | /24 block |
|---|---|---|
| 111.124.200.109 | Website | 111.124.200.0/24 |
| 42.186.102.226 | Name server ns5.nease.net, Name server ns2.nease.net | 42.186.102.0/24 |
| 54.228.156.72 | Name server ns6.nease.net | 54.228.156.0/24 |
| 18.182.82.158 | Name server ns8.nease.net | 18.182.82.0/24 |
| 8.147.116.45 | Name server ns4.nease.net | 8.147.116.0/24 |
| 42.186.168.126 | Name server ns1.nease.net | 42.186.168.0/24 |
| 182.92.22.240 | Name server ns3.nease.net | 182.92.22.0/24 |
| 111.124.200.35 | Mail server mx.ym.163.com | 111.124.200.0/24 |
WHOIS of the domain icourse163.org
Domain Name: icourse163.org Registry Domain ID: REDACTED Registrar WHOIS Server: whois.pir.org Registrar URL: http://whois.pir.org/ Updated Date: 2026-08-12T01:58:56Z Creation Date: 2014-02-25T06:41:39Z Registry Expiry Date: 2027-02-25T06:41:39Z Registrar: Alibaba Cloud Computing (Beijing) Co., Ltd. Registrar IANA ID: 420 Registrar Abuse Contact Email: [email protected] Registrar Abuse Contact Phone: +86.95187 Domain Status: clientUpdateProhibited https://icann.org/epp#clientUpdateProhibited Name Server: ns1.nease.net Name Server: ns2.nease.net Name Server: ns3.nease.net Name Server: ns4.nease.net Name Server: ns5.nease.net Name Server: ns6.nease.net DNSSEC: unsigned URL of the ICANN Whois Inaccuracy Complaint Form: https://icann.org/wicf/ >>> Last update of WHOIS database: 2026-10-01T23:16:15Z <<< For more information on Whois status codes, please visit https://icann.org/epp Terms of Use: Access to Public Interest Registry WHOIS information is provided to assist persons in determining the contents of a domain name registration record in the Public Interest Registry registry database. The data in this record is provided by Public Interest Registry for informational purposes only, and Public Interest Registry does not guarantee its accuracy. This service is intended only for query-based access. You agree that you will use this data only for lawful purposes and that, under no circumstances will you use this data to (a) allow, enable, or otherwise support the transmission by e-mail, telephone, or facsimile of mass unsolicited, commercial advertising or solicitations to entities other than the data recipient's own existing customers; or (b) enable high volume, automated, electronic processes that send queries or data to the systems of Registry Operator, a Registrar, or Identity Digital except as reasonably necessary to register domain names or modify existing registrations. All rights reserved. Public Interest Registry reserves the right to modify these terms at any time. By submitting this query, you agree to abide by this policy. The Registrar of Record identified in this output may have an RDDS service that can be queried for additional information on how to contact the Registrant, Admin, or Tech contact of the queried domain name. Domain Name: icourse163.org Registry Domain ID: REDACTED Registrar WHOIS Server: whois.pir.org Registrar URL: http://whois.pir.org/ Updated Date: 2026-08-12T01:58:56Z Creation Date: 2014-02-25T06:41:39Z Registry Expiry Date: 2027-02-25T06:41:39Z Registrar: Alibaba Cloud Computing (Beijing) Co., Ltd. Registrar IANA ID: 420 Registrar Abuse Contact Email: [email protected] Registrar Abuse Contact Phone: +86.95187 Domain Status: clientUpdateProhibited https://icann.org/epp#clientUpdateProhibited Name Server: ns1.nease.net Name Server: ns2.nease.net Name Server: ns3.nease.net Name Server: ns4.nease.net Name Server: ns5.nease.net Name Server: ns6.nease.net DNSSEC: unsigned URL of the ICANN Whois Inaccuracy Complaint Form: https://icann.org/wicf/ >>> Last update of WHOIS database: 2026-10-01T23:16:15Z <<< For more information on Whois status codes, please visit https://icann.org/epp Terms of Use: Access to Public Interest Registry WHOIS information is provided to assist persons in determining the contents of a domain name registration record in the Public Interest Registry registry database. The data in this record is provided by Public Interest Registry for informational purposes only, and Public Interest Registry does not guarantee its accuracy. This service is intended only for query-based access. You agree that you will use this data only for lawful purposes and that, under no circumstances will you use this data to (a) allow, enable, or otherwise support the transmission by e-mail, telephone, or facsimile of mass unsolicited, commercial advertising or solicitations to entities other than the data recipient's own existing customers; or (b) enable high volume, automated, electronic processes that send queries or data to the systems of Registry Operator, a Registrar, or Identity Digital except as reasonably necessary to register domain names or modify existing registrations. All rights reserved. Public Interest Registry reserves the right to modify these terms at any time. By submitting this query, you agree to abide by this policy. The Registrar of Record identified in this output may have an RDDS service that can be queried for additional information on how to contact the Registrant, Admin, or Tech contact of the queried domain name. % Query time: 1155 msec % WHEN: Thu Oct 01 23:16:14 UTC 2026