The new Gmail interface is slow. Man, it's just so freaking slow. The fans get whirring, the network calls are probably blocked by the UI and if you delete a message and quickly close the page it never goes through.

Thunderbird struggles with managing and searching large mail archives in a way that Gmail doesn't. I use Thunderbird for a work email account, and its GUI thread regularly gets blocked while trying to search or open messages.

To be fair, my work email account is an exceptional case - it's got somewhere around ~1 million emails.

Gmail, particularly with the new Gmail interface launched a few months ago, also sucks performance wise, but in different ways from Thunderbird.

> Gmail lags severely compared to when I use Thunderbird.

The number of times where I am typing an email and somehow trigger hot keys is absolutely ridiculous. Mid-word and suddenly I've deleted the draft, changed labels, and muted & archived a critical conversation is absolutely infuriating. It's Outlook level bad.