Very benign matter - preferred title

[MQv2]

Currently involved in a project which involves emailing a lot of people who I have not spoken with before.
Not cold calling.
Just wondering where it is evident that the recipient it female is the proper ettiqeute to use Mrs or Ms?
I know it's a small matter but I'd rather make sure that I'm not causing any annoyance.

Or even Dear Madam/Sir

Got to challenge the patriarchy whenever you can!

if in doubt, I've been taught to use "Ms"

I would go Ms rather than Mrs/Miss but like others my instinct would be to try and avoid the situation if at all possible by going for Dear Firstname Surname or Dear Sir/Madam. The Ms/Mrs issue is so divisive you always end up pissing someone off.

""I know Ms used to associated with being divorced"

Why, that's neither it's origin nor much of it's use!

I think Ms definitely has local interpretations - where I grew up, it was used for the divorced, and when it was used by a woman who had not been married before, she was "up herself", "no better than she ought to be" and "possibly one of those women". Or possibly that was just my mother's view As a kid I found it wildly exciting to uncouple yourself from your marital status.

Overall I would prefer to be addressed as Ms by a stranger; to me it's less presumptuous than Miss/Mrs and more formal than first name last name. I am generally uncomfortable with people using my first name in a formal situation anyway (I do hate it when the bank phones and uses my first name, since I haven't consented to that level of informality), and since I work in schools it's formal usage nearly all the time anyway.

I find Dear Firstname Surname a bit weird in emails - back when we still wrote letters, it wouldn’t have been used to start one. To me it makes the email sound like spam!

I would go either Dear Firstname or “Ms” for women.