What is responsible mail addr in nslookup

In nslookup, the -r or --responsible option is used to specify a responsible mail address. This option is used to query the DNS for the responsible mail server for a particular domain or hostname.

When you use the -r option, nslookup will send a query to the DNS server asking for the responsible mail server for the specified domain or hostname. The responsible mail server is the server that is responsible for handling email for that domain or hostname.

The responsible mail server is typically the mail exchanger (MX) record for the domain or hostname. The MX record specifies the mail server that is responsible for receiving email for that domain or hostname.

Here's an example of how you can use the -r option with nslookup:

nslookup -r example.com

This will query the DNS for the responsible mail server for the example.com domain.

The output will typically include the mail server's hostname and IP address, as well as the priority and preference values for the MX record. For example:

Server:         ns1.example.com
Address:        192.0.2.1

Non-authoritative answer:
example.com      mail exchanger = 10 mx1.example.com.
example.com      mail exchanger = 20 mx2.example.com.

In this example, the responsible mail server for the example.com domain is mx1.example.com with a priority of 10, and mx2.example.com with a priority of 20.

Note that the -r option is not available in all versions of nslookup. In some versions, you may need to use the set type=mx command to query for the MX record, and then use the server command to specify the DNS server to query. For example:

nslookup
> set type=mx
> server ns1.example.com
> example.com

This will also query the DNS for the responsible mail server for the example.com domain.