Define the company you are interested in, its structure, perhaps a subdivision of the company, its location (country, city, district).

Define the positions of the persons of the company who may be interested in your proposal. If there are no required email contacts at the official website:

Register at some popular career-oriented social networking site like Linkedin, XING etc.

Open e.g. Linkedin website.

Insert the name of the company you are interested in in the search window.

Choose “<the name of the company> in people”.

Choose location (country, city).

Register at some email verification tool (e.g. Lusha, GetEmail.io, etc.).

Bound Lusha to Linkedin or XING etc.

Choose a person who can concern your offer directly or indirectly (e.g. Document Controller/Coordinator, Sales, HR, Support, Distribution, Internal Language Services, Executive Officers, Project Managers).

Lusha will show you the email and phones for the first 5 persons automatically free of charge.

From the 6th person you will be showed only the email extention unpaid.

Take on the showed extention and construct the emails for the persons of the given company by analogy.

Email construction can involve the substitution of different variants of writing, e.g.

“first_name.surname@extention”, “first_letter_of_the_first_name.surname@extention”, etc.

Send a constructed email for a test. If it is not returned after a while, send the by analogue constructed emails to other persons of that company.

https://rocketreach.co/ or try to search in Google “company name rocketreach” and see the results.