Update: The Sparrow guys tell me they’ve found and nailed the bug, and will release the fix in 1.4 in late September.

I’ve just discovered a critical issue with Sparrow that I thought others should be warned of. It just bit me, big-time, when in the middle of an important negotiation with a third party, an earlier unpolished draft was sent out instead of the final email, when I experienced a momentary Internet connection dropout.

Sparrow has an issue where hitting “Send”, in unreliable network conditions, on a draft message that has been modified, results in a prior copy of the message being sent, rather than the latest version.

To replicate this issue reliably:

1. Create a new message (Cmd-N)
2. Specify a recipient (oneself), subject, and some body content (say, the letter “A”)
3. Hit “Save”, to save the draft
4. Change “A” to “B”, then disconnect the network connection (in my case, turning off the radio on my external WiFi adapter), then hit “Send”. Sparrow will report a failed connection, and will keep the outgoing message with state “Pending”
5. Restore network connection. Upon detecting the restored connection, Sparrow will proceed to send the message
6. Check email. Received test email will have “A” in the email body.

Scary stuff. I hope they’ll fix this soon, but it’s going to make the app difficult to trust in future!

Update: I should mention, a probable workaround for this is to never, ever hit “Send” until you’ve saved the draft, and verified that the save operation has completed (perhaps even restart the app first).