Pick Dodosend if…
Your mail is all Gmail
Mailbird reaches Gmail over IMAP, so IMAP has to be on and labels show up as folders. Dodosend works with Gmail itself: labels stay labels, and from: or has:attachment work as they do in Gmail.
You’re on Linux
Dodosend has a Linux desktop build, as an AppImage, a .deb and an .rpm, next to macOS and Windows. Mailbird is for Windows and Mac.
You’d rather not touch the mouse
Every action in Dodosend has a key, ! shows the ones for the screen you’re on, and ⌘K (Ctrl+K) opens a palette for the rest that reads “remind me fri 10”.
You want every feature for free
Dodosend’s Free plan has everything for one Gmail mailbox: reminders, scheduled send, the calendar. Mailbird’s free version covers one account, with its Premium features as a trial.