The simplest way to write a brief email is using Siri, which is described in the Siri essentials page on this website. I certainly don't recommend using Siri to compose long emails. The page you are reeding will describe how to write an email using the Mail app. This will allow you to type, dictate, handwrite or use Braille Screen Input to enter the message and its subject. These text input methods can be used in any combination; you might dictate text that is easy for dictation to interpret and switch to typing for the more difficult words. You will also be able to use VoiceOver's text editing features to make corrections.
Entering email addresses can be fiddly and I recommend that you ensure that you need to enter email addresses only once by recording email addresses as well as phone numbers in your Contacts.
The instructions that follow assume that VoiceOver is turned on.
Open the Mail app. The "compose, button" that is used to write an email message is at the bottom right of all major screens in the Mail app. If you can't find the compose button, the Mail app may have been left with an incomplete task. look for a done button or a cancel button at the top of the screen and double tap to dismiss the incomplete task.
After you double tap to activate the compose button you should hear VoiceOver speak "Too, text field, is editing". This means that the app is waiting for you to give it an email address for the recipient of the message.
The next step is a little odd. You usually need to swipe left to find the "add contact" button and double tap. Occasionally, this button is moved and you may need to swipe right to find it. It's definitely either one swipe left of the Too field or one swipe right. This will bring up a screen showing all your contacts. If you don't have many contacts, just keep swiping right until you reach the correct contact and then double tap. That will add the contact to the Too field. You may hear the word "dimmed" spoken after some contact names. This indicates that you have no email address for that contact and you will not be able to select it.
If you have a lot of contacts, you should use a different approach for finding the desired contact. Swipe left, or perhaps right, from the Too field to locate the "add contact" button and double tap to activate it. Then swipe right until you hear VoiceOver speak "section index, adjustable". Alternatively feel for the section index at the extreme right centre of the screen. The section index is placed along the extreme right edge of the screen and is like the alphabetical tabs on an old-style address book and the word "adjustable" is VoiceOver's way of telling you that you can progress through the alphabet with a swipe down. Swipe down with one finger to go through the letters until you reach the letter you need for the contact's surname or first name. Contacts may be ordered either by first name or surname. This is set in Settings / Apps / Contacts. Now swipe right and you'll work your way through all the names beginning with your chosen letter. Double tap when you've found the right contact and it will be placed in the Too field.
The email address of the recipient is now entered and you may have heard "Subject, text field, is editing". If you didn't hear that swipe right until you reach the Subject field and double tap to begin editing the subject. Whenever you hear VoiceOver speak "text field, is editing" you will be able to enter text. But if VoiceOver doesn't say "is editing", double tap to begin editing the subject.
You should now enter the Subject. This should be a brief description of the purpose of the email message.
When you have finished entering the subject of the email you need to move to the "message body" part of the screen where you can enter the email message.
Swipe right until you hear "message body, sent from my iPhone". "Sent from my iPhone" is the standard text that the Mail app inserts at the end of all your messages. Double tap to start editing the message body. You will probably hear "insertion point at start". If you don't hear this double tap repeatedly until you do.
Now enter your message.
When you have finished writing your message then it's time to find the send button near top right of your screen and then double tap to send your message.
You may, of course, make mistakes when you enter your email message. You can fix them if you spot them as you type or handwrite by using the delete key or swiping left with two fingers for handwriting. If you spot errors later, then you will need to do some editing with VoiceOver. See Simple text editing with VoiceOver. If you use dictation to write the message consider dictating in short burst so that if something goes wrong you can undo the last burst of dictation and keep the rest. Unless you have it turned off, shaking your iPhone will bring up an undo alert. Swipe right to find the "Undo" button and double tap.
When a recipient is entered, VoiceOver may move its focus to the Subject. If this happens, for each additional recipient you must swipe left repeatedly to locate the Too field and double tap to edit it again. Then swipe left to locate the "add contact, button" to add another contact. Alternatively, as you swipe left from the subject field you will also encounter a cc/bcc button that can be used to add a recipient for a copy or blind copy. To do this, double tap on the cc/bcc button and you will probably hear "cc, text field, is editing". If you want to enter a contact as a cc swipe left repeatedly to locate the "add contact, button" and add the contact as for the Too field. If you want to add a bcc contact, swipe right after hearing "cc, text field, is editing" and you will hear "bcc, text field". Double tap to start editing the bcc field and swipe left repeatedly to find the add contact button as before.