Open the Mail app either by instructing Siri to "Open Mail" or by locating the Mail app on the home screen and double tapping.
Apps usually start where you last left them, so it's not possible to be precise about what will be on the screen when you open the Mail app. It's most likely to be in one of two states.
The app will probably either be displaying the list of emails in your inbox, giving a brief summary of each email, or it may be displaying a single email filling the screen.
If the app is displaying the list of inbox emails then the "back" button at the top left of the screen will speak "mailboxes, back button" or possibly the name of a specific mailbox, for example b t internet. This is the screen you need if you want to skim efficiently through your email messges.
If the mail app starts with a single email on the screen then the back button at top left will speak something like "inbox, back button". Selecting that and double tapping is the way to get back to the inbox list, which is where you need to be if you want to skim efficiently through your emails.
Let's see how to skim through your inbox, quickly delete unwanted emails and open emails you want to read in full.
Swipe right past any initial buttons and headings after which VoiceOver will speak the first, most recent, email in your inbox. As VoiceOver moves from message to message in your inbox it speaks a brief summary of each message. This will include the name of the sender, the subject and the beginning of the email message. You can skim through summaries of the emails in your inbox by swiping right to hear VoiceOver speak the summaries one by one. VoiceOver will let you know if a message has attachments and speak the number of attachments. The summary may be sufficient to let you decide that you want to delete the email. Swipe up with one finger until VoiceOver speaks "delete". Double tap and VoiceOver should report "message deleted" and then speak the summary of the next email.
When you have reached an email that you want to read in full, double tap anywhere with one finger and the email will fill the screen and VoiceOver will speak the start of the email.
To hear the email spoken in full swipe down with two fingers.
To pause and resume the speech, tap the screen with two fingers.
When you have finished reeding that email, slide your finger near top left of the screen to find the "inbox, back button" or a similar back button and then double tap with one finger to return to the list of items in your inbox. An alternative to finding the back button and double tapping is to perform a two finger scrub gesture. This is drawing a letter z with two fingers. This usually works as an alternative to locating and double tapping a back button.
An alternative way of working through your email is to remain with an email filling the screen. Find the "inbox, back button", near top left of the screen and then swipe right and you'll find "previous message" and "next message" buttons that may be double tapped to move through the inbox. If you slide your finger near bottom left of the screen you will find the "delete, button", which should be double tap if you want to delete the current message.
An email may include one or more attachments. Here is how to read email attachments.