Not a question or query. I was composing a speculative letter in Thunderbird which was eventually to have a PDF attached (a portfolio of my work). The body of the letter contained the phrase 'please find attached my portfolio as a PDF'. Anyway, I wanted to test some text formatting first and sent the mail to another of my accounts without the attachment.
Thunderbird flagged the word 'attached' and asked if I had forgotten the attachment! I hadn't because of the test I was doing but I thought that was quite neat.
A couple of times I've forgotten to attach my CV when making job applications
Not sure if this is a common feature in most email apps. A nice touch anyway.