This is using formal Business English. This sentence means: they do not accept CVs from people who have general interest in applying for a job. They ONLY accept CVs for specific jobs that are available at the company. If I send them my CV because I am curious about possible job openings in the future, they will not read or save my CV.
Some industries are okay with "speculative applications." Here is a description I found online from Oxford University's Career Center. Their advice is:
(1) Speculative approaches to employers are useful, and often essential, for gaining:
- Work in employment areas in which vacancies are rarely advertised (eg journalism, broadcasting, publishing)
- Vacation work
- Unpaid work experience or work shadowing
- Some sectors recruit more at different times. TV companies, for example, tend not to recruit many people in the middle of winter. Try to find out from contacts at what time of year your application is most likely to get noticed!
(2) A speculative application usually consists of a CV and letter, but could be preceded or followed up with a telephone call. A few pointers:
- Identify your target (by researching employers and talking to people about their jobs).
- Write to a named individual if at all possible.
- Tailor-make each approach, showing how your experience and achievements are relevant.
- Make it clear what you have to offer them. You are making a business proposition, and must prepare your case carefully and research the organisation.
Hope this helps!