Mailspring keeps a local cache of your mailboxes, so you can keep working when your connection drops: read messages that have already been synced, search them, compose new mail, and schedule messages as usual.

Message bodies, images, and attachments are available offline only if Mailspring has already downloaded them — that is, if you opened the message (or it arrived recently) while you were online. Older messages that were never opened may show only their headers until you reconnect.

Messages you send while offline are queued and go out automatically when you reconnect. Actions like archiving, labeling, and moving are queued the same way and applied to the server as soon as Mailspring is back online.

When Mailspring can’t reach your mail server, it shows an alert in the bottom left of the main window and reconnects on its own once the network is back. See Checking for new mail.