to whom it may concern; to all parties concerned
A formal salutation used in business letters, emails, or announcements addressed to multiple relevant recipients. Conveys respect and is typical in official or corporate contexts.
To all concerned, thank you for taking time out of your busy schedules to attend.
I sent the email with 'To whom it may concern' at the beginning.
各位 is a formal plural suffix meaning 'all of you' or 'everyone', used after titles or group names. 関係者各位 specifically addresses all involved parties.
ご担当者様 is a common salutation meaning 'Dear person in charge', used when the specific recipient is unknown. 関係者各位 is broader, addressing all relevant persons.
Compound of 関係者 (kankeisha, 'concerned parties') and 各位 (kakui, 'everyone' or 'all of you'). 各位 is a formal plural suffix used in written addresses.