The developers are aware of performance issues. Typically when the local folder size is set to a high number of messages or a large number of accounts are present. They are working on refactoring the app which should improve this is a future release. If you have the local folder size set to a high number of messages, try reducing this. '''Settings > account name > fetching mail: local folder size''' '''Reference:''' https://github.com/thunderbird/thunderbird-android/issues/10373#issuecomment-3810077139 ---- ''"The app's performance slows down when many messages are downloaded. This is because it currently loads all messages into memory at once."'' ''"I tested this and performance begins to degrade noticeably once the message count exceeds 500. This is worse than tought, we need to improve the message handling. Propably database related, but the message list refactor could help too."'' ---- '''Reference:''' https://github.com/thunderbird/thunderbird-android/issues/10409#issuecomment-3811149422 ''"We recognize that the performance and loading times of the Message List are not optimal. We are currently working on a refactor to ensure the app runs smoothly, even when managing multiple accounts."''

Thank you @Platform34 for answering. I tried to reduce my number of messages in the folders : It didn't change anything in terms of velocity It is not a major issue as I finish to receive messages