Mail deletes inbox message after reply

Yes, the sent folder shows the reply, and sometimes the first part of the thread, but no attachments.

It seems inconsistent: yesterday I had one that behaved as I described, but today I had one that didn't.

It's a gmail account, and I am using POP, not IMAP - much better for those poor internet times. Messages, once downloaded, should stay on my iMac until I explicitly do something with them - the email server in the sky shouldn't have any effect on them. One characteristic of such an account is that sent messages are reflected back by gmail and appear as a new inbox message, and this is useful in that I can see messages that my wife sends (same email address, different device).

This message reflection is clouding the issue, and when I just started to try and accurately characterise the problem, the exact behaviour wasn't obvious. Unless there is anything obvious I can try now, I will start to keep a log of occurrences and try to pin it down more carefully. Then I will make a new post.

Thanks.

Paul.