Gmail question: deleted messages keep coming back

I've finally moved from Hotmail to Gmail and I've resolved most of the annoyances except this one: many of the messages I delete from my inbox reappear in my inbox a day later. I've Googled and tried some of the easier (non-programming-type) fixes suggested online but it's still happening. What am I doing wrong?

Are they in your Inbox or are you viewing All Messages (which includes those in the Trash)?

They're in my Inbox.

Have you deleted your hotmail acct?

Did you migrate your hotmail to gmail using gmail?

Do you have a forgotten forward rule somewhere?

Did you check the box that said leave a copy on the server?

Are you using an app or web?

I followed the steps given by gmail to migrate a Hotmail account to gmail. Since I don't want to notify hundreds of contacts to use my new gmail address, I decided to forward Hotmail indefinitely to gmail rather than shut the old account down. I think I'm using the browser version.

Other puzzling details are that not all my deleted messages return from the grave, and deleting them once more seems to kill them permanently. It's the Undead Inbox, lite version.

As you've noticed messages are grouped into threads. When you hit Delete, you are archiving them. When a new reply arrives that goes with an old thread, the thread is pulled out of the archive. You could turn off the threading option, though I suggest you don't do that hastily. In time, you will see the benefits of it.

So there's no way of stopping this? Can't I delete instead of archiving?

You could make a filter for it. That's under Settings. Filters take some effort to set up, but you'll be impressed at how they save trouble in the long run. As a colleague of mine used to say, if you are not using email filters, you are working too hard. I receive literally thousands of emails a day, but gmail is configured to present the most important ones. Sometimes I look at the others, and sometimes I don't, depending on my time and mood.