How to organize a simple reception of letters on the server for the domain?

Question

Mail server

Hello! At the moment, there is a server (ubuntu 18.04) and the correct sending of emails on behalf of the domain (sendmail + opendkim) is configured. Now the question arose of receiving letters, and as far as I understand, there are two options:
1) use other people's smtp servers to send and receive letters (for example, google)
2) organize the reception of letters on the server with all the consequences (spam filtering, dos, client for display)
If fully use google for sending / receiving, as far as I know it is paid for domains, is there any option to leave the current sending of letters and forward all incoming letters to, for example, a gmail account so that it filters spam or is it impossible? Or there are some other options, you just need to accept letters to one address in the domain
UPD: Solved using a free external mail service (Yandex for domains), for this, just an MX record is registered in the DNS of the domain

Answer 1

You can send as you wish.
If you need to take. Yandex, Mail, ....., paid mail hosting, own server

Answer 2

is there any option to leave the current sending of emails and forward all incoming emails to, for example, a gmail account,

there is. true choice of sendmail in 2019 as MTA...