Which email marketing service is safe to use (that won't spam my subscribers with their spam)?

Question

Email

Our company is engaged in live broadcasts from various promotions and we want to make it possible to subscribe to notifications of new broadcasts that will be sent by e-mail. The estimated size of only the existing part of the audience that is most likely to subscribe to such a mailing list is already beyond the limits of Yandex Mail for Domains (no more than 35 emails per day sent via SMTP) and Gmail for mailing lists .
You can tinker with your own exim settings, but it's just constant, endless hemorrhoids and a headache with emails getting into spam, especially in Gmail (about PTR, SPF, Precedence, List-Unsubscribe, DKIM, DMARC, Message-ID, Date, FBL and etc. I know).
I absolutely did not want to use mailing services, but it seems that there is no choice left. Why I didn’t want to: I’m most worried about the privacy of the subscriber base, I want to have a reinforced concrete, 146% guarantee that the service will not start spamming our subscribers with its own separate spam, or, moreover, will sell the base to third parties. Therefore, we need someone with experience who has already worked with mailing services and is confident in some specific services, confident in their reliability. Would you recommend such services?
From additional wishes: the presence of an API so that you can send a letter to the mailing list not through some kind of web interface; the ability to substitute your own domain (@news.domain.com) in the “From” address of the mailing list.
We are not chasing the lowest rates, because the distribution is rare (5-10 letters per month) in terms of the size of the base, which even in the future is unlikely to exceed 5,000 addresses.

Answer 1

Our guys use Unisender.