“I was asking as a club secretary who regularly E-Mails to members.
Does that make it clearer?”
Yes it does and my earlier answers are not appropriate.
First of all, you may be required to register with the Information Commissioner’s Office. It is unlikely, especially if you are a small “Not for Profit” organisation. There is an assessment questionnaire here which makes the decision for you:
https://ico.org.uk/for-organisations/register/self-assessment/
However, processing or holding data as secretary of a club obviously moves away from “…the purposes of that individual’s personal, family or household affairs (including recreational purposes)”. So even if you do not have to register you must still comply with the Data Protection Principles since you hold “sensitive personal data” of living individuals. E-mail addresses are included in this (since, by themselves or together with other data, they can be used to identify living individuals). You must keep this data safe and obviously distributing it in the form of an e-Mail distribution list does not keep it safe. So I believe the ”Bcc” option mentioned by others should be employed.