In DNS-zone of the second-level domain (on hosting provide side) insert CNAME-record where
CNAME is a type of record.fwd.getcourse.ru - record value (some providers require a dot at the end of a value, some providers add it automatically).
fwd.getcourse.ru - record value (some providers require a dot at the end of a value, some providers add it automatically).
After setup of redirection of sub-domain according to CNAME you won’t be able to set up a mailing with usage of this sub-domain. You have to use second-level domain in this case. For example, you have domain.ru (the domain itself) and course.domain.ru (the sub-domain). The sub-domain is redirected to CNAME. Then when setting up mailings you need to use either domain.ru or some other domain.
If the second-level domain is added to an account as well as third-level domain, and your account is opened with both ones, contact our technical support teamto set up authorization with usage of both domains.