That may vary by hosting provider and by service band. (You have to pay more for customisation capability iirc)
If you decide to DIY, this is totally at your discretion and free.
Bear in mind there are other options, like Vultr, Scaleway, Hetzner, Linode, AWS …
I found a provider that offered a free service up to a certain capacity (Sparkpost). Shop around (Mailgun etc.).
It’s very important you use a good brand for mail provider as that will help the trusted delivery of your email.