Is there a service for sending emails for online stores (not mailing)?

Question

Email

We often have a problem that letters sent by an online store (website) do not reach gmail.com, and often do not reach mail.ru either.
Are there any services that will allow them to send daily letters (your order is accepted, your order is processed, and so on, not mailing) so that the letters are guaranteed to reach.

Answer 1

There is. Such letters are called transactional. You can google domestic services. Western examples: Mandrill and Sendgrid.

Answer 2

And there is Yandex mail for the domain. With the correct SPF setting (you need to add your server's IP in addition to Yandex ones), everything works like a clock. For free.
Quote from https://help.yandex.ru/pdd/records.xml

If you want to send emails not only from Yandex servers, you must list these servers in the SPF records. Instead of “v=spf1 redirect=_spf.yandex.net”, you must specify the following value: “v=spf1 ip4:IP-1 ip4:IP-2 ip4:IP-3 include:_spf.yandex.net ~all”, where IP -1, IP-2, IP-3 — addresses of those servers from which letters are additionally sent.