We stared to test the best way to send outbound and often we do not recommend to hurt your master domain so for example at Saleshub.ai we use saleshubai.com for outbound email and we do it totally free here is how:
Step1. First go to https://mail.yandex.com make an account
Step 2. go to https://connect.yandex.com/ then go to https://admin.yandex.ru/domains and add your domain
Step 3 Add users with the email addresses you like on https://admin.yandex.ru/users using your new domain
Step 4 follow this to setup IMAP AND SMTP https://yandex.com/support/mail/mail-clients.html
Step 5 you are good to go
Their daily limits are here:
If you wish to go beyond these limits we recommend on your extra domain to use IMAP from Yandex and make an SMTP account with Sendgrid to exceed these limits.