if you're looking for free outbound tools, this list might help:
https://www.namepros.com/threads/outbound-list-of-free-tools-to-help-with-outbound-sales.1352033/
It depends on how many leads you can find for the targeted niche. There's no minimum or maximum.
Though, you'll want to space your emails out and not blast a bunch all at once, otherwise you risk getting your email flagged.
It's hard to suggest a catch-all email template if you have multiple domains in different niches. Most your emails will need to be customized for the niche you are targeting and for the specific business model the domain is intended to be used for.
If you really want something generic to start with, maybe:
Subject: Quick question about [CompanyName]
Body:
Hi [First Name],
I came across your business and thought you might be interested in acquiring a domain that could enhance your brand visibility and online reach.
The domain [DomainName.com] is currently available, and I believe it aligns well with your industry and audience. Itโs short, memorable, and could be a strong asset for marketing, SEO, or future expansion.
If this is something you'd consider, Iโd be happy to share pricing and answer any questions.
Best regards, [Your Name] [Your Contact Info] [Optional: Website or LinkedIn]
The above is not the best template, it needs to be customized for each domain name after you research the person or company you'll be contacting (Adding vital information they can relate to about their own business and potentially, niche competitors).
You probably should have researched that prior to acquiring it.
At any rate, the best thing to do is to try and identify at least 5 different business models that could work with the domain you acquired and then you can try to identify leads in the most practical niche out of the 5 using some of the free tools I linked you to above.
Here's an example break down I provided for someone else to give you a better idea of what I mean:
https://www.namepros.com/threads/cc1-org-why-cant-i-sell-this-for-even-400.1359174/post-9432684
Good luck!