The Thunderbird app doesn't store emails and data on their own server/cloud . It connects to your email provider's server/cloud. For example Gmail, Microsoft, Yahoo etc. Who is your email provider? If you used Thunderbird Mobile on your old phone, and connected using the [https://geekchamp.com/imap-vs-pop3-whats-the-difference-which-one-should-you-use/ IMAP Protocol] your emails will still be on your email provider's servers. Once you add your account to the app, your emails will download. '''To add an account''' # Open the mobile app. # Click start. # Click add an account now. # Enter your email address. # Click next. Thunderbird will try and automatically detect the connection settings. If successful ... # Enter your password, or if using oAuth authentication, click Sign in with [provider] button. # Complete the login steps # Upon successful authentication, your emails will download. If you used the [https://geekchamp.com/imap-vs-pop3-whats-the-difference-which-one-should-you-use/ Pop3 protocol] on your old phone, your emails might be lost unless you configured your email provider settings to keep a copy on the server. Pop3 stores emails on the local phone/PC, not the server by default.