Hi. I use the Thunderbird program many years. Since November 2022 I have problems with the deliverance of my messages to some people. Usually, it concerns the users of the same domain mail.ru: I send them a letter 2-3 times via Thunderbird because they do not get it. The browser works correctly, so the problem is only with my messages via the post program. It is not comfortable, I lose a lot of efforts in order to check whether my respondent has got my message or not etc. How to improve the service?