i want to know about "m" of marketing.

As a marketer of a design corporations, recently I think it is hard to market something. Of course, there is nothing easy in the world, it is a really hard thing. If I send a message to one design company, they say "don`t spam me". My major is not marketing or economics. So it is hard? Anyway I want to know about " the effective way to send a letter or P.R" .Please give me your tips or method.

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