Use sentAt as the default date for sorting messages instead of receivedAt

[Area128]

I know that the "Message list order" setting exists and once the Date sent option works, one can set it to whatever they like. However, here are a few quick reasons why sentAt should be considered as the default:

• SMTP is not a real time protocol. The safeguards involve multi-day holding queues before a message is delivered
• Sys admins like seeing event messages in the order they happened, especially around the time of outages when delays are more likely to happen
• "No boss, I didn't wait 2 days. I replied to your message within 5 minutes but the mail server delayed it"
• Convention. Pick any other mail client, they all seem to default to date sent as the sort by date

Would be interested in hearing your views.