In order to avoid problems when sending bulk email to subscribers on Mail.Ru servers, send relevant and necessary messages to real people who are really interested in receiving them.
Also, be sure that the messages being sent and the means of delivery correspond to generally accepted technical standards.
Here are a few recommendations with regard to sending messages to Mail.Ru:
Note that these recommendations are designed to reduce the number of user complaints and, consequently, improve your reputation as a sender. However, compliance won't keep your messages from being checked by anti-spam filters.
Register your domain with Postmaster@Mail.Ru to monitor and improve quality of your mailing lists.