* The question asks about the command that an engineer should send before entering the DNS name to verify the external record for SMTP traffic, which is the mail exchange (MX) record.
* The MX record is a type of DNS resource record that specifies the mail server responsible for accepting email messages on behalf of a domain name.
* To query the MX record using the nslookup command, the engineer should first set the query type to MX using the command set querytype=Mx or set type=Mx.
* The other options are not correct, as they do not set the query type to MX:
* set type=A sets the query type to A, which is the address record that maps a domain name to an IP address.
* ls -d company-mail.com lists all DNS records for the domain company-mail.com, but does not specify the query type.
* set domain=company.mail.com sets the default domain name to company.mail.com, but does not specify the query type. References:
* CompTIA Network+ N10-008 Study Guide, Chapter 3, Section 3.4, DNS Concepts, page 1441
* Professor Messer's CompTIA N10-008 Network+ Course Notes, Section 3.4, DNS Concepts, page 242
* Professor Messer's CompTIA N10-008 Network+ Training Course, Video 3.4 - DNS Concepts, 9:00 -
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