AltaMail will optionally group together all email that has the same subject line and the matching header fields. This means you can quickly read through or action all emails that belong to the same conversation string.

You can turn threading on or off in the app settings (View) - Email Management section - Email Threads. You can choose to link by subject, as well as normal replies. You can include sent emails in threads. You can ungroup email threads by turning off this setting.

When you are viewing an email conversation, you can swipe on each email to apply actions to that email. Tap on the expand ("...") button to view more detail about each email in the thread.

Hint: There is also a quick way of actioning or deleting an entire email thread while in Inbox view. Double tap on the check box beside the top email in the thread and all subsequent emails in the thread will be shown and checked too.
Now you can swipe or choose an action to apply to all of the selected emails.