Feature request: adding labels to mails

K9 mail is an amazing app. Here’s my idea to make it even better - ability to add labels to mails. I’ve got 3 mail accounts for different purposes and very often in need to open messages few times to remind what they were about. Imagine people who run multiple companies.
Frequently mails have unclear titles and adding labels would make productivity better.

Hmmm.

Labels might be quite a beast as there is no good way to store them along with the mail on the IMAP server and no way to do so on a POP3 server. This would mean that K9 mail would need to store the labels in a separate database and hope that it always manages to mapltch the right entry in its internal database with the right mail: Mails tend to have id numbers that allow to recognize exactly this mail. But those IDs tend to to be unique, sometimes.

Alright. We can always go to settings and set preview lines number to show more message content.