What is the best service to use to send messages by mail through a web application?

Question

Email Marketing

I am developing a web application for recording a client to a master. After recording, information about the visit is sent to the client by mail, but after two days of testing, as I connected, I was banned for spam in my opinion. My django application returned: 554, b'5.7.1 [2] Message rejected under suspicion of SPAM https://ya.cc/1IrBc
Used mail from Yandex.
It turns out that you need to use special mail services for mailings so that you don’t get spam? If I use google or mail.ru will I also get banned for spam?

Answer 1

All mailers sooner or later can block such a scheme. Moreover, if you write to them, they will answer something like - our mailboxes are not intended for mailing, use specialized services.
And here there are already options. At least three. You can set up your own server on the VPS and send through it.
You can use any of the mailing services.
Or use paid SMTP servers. And they all usually have big free packages for a month, so it all depends on the volume, maybe a free option.
In general, I analyzed this topic in this article
https://7fk.ru/nastroyka-smtp/

Answer 2

Google, mail.ru, Yandex and others like this are for personal mail, they are very against transactional emails. Look towards Amazon SES, SendGrid, Mailgun and the like.