where are "Send later" Emails saved? are they backed up?

Greetings KenienS, 

When deleting emails, one place we’d recommend checking is the Trash folder on your device and for your specific email account. 

You can also try to search for the email, to see if it’s showing in another mailbox, such as Trash - Search for email in Mail on iPhone

Search for text in an email

1. From a mailbox, swipe down to reveal the search field, tap it, then type the text you’re looking for.

2. Choose between searching all mailboxes or the current mailbox above the results list.

3. Tap search, then tap an email in the results list to read it.

Mail searches the address fields, the subject, the email body, documents, and links. The most relevant emails appear in Top Hits above the search suggestions as you type.

Thanks. 

Hello KenienS,

After deleting an email from the Send Later folder, they are moved to either the Archive or Trash folder of your account. It would depend on how you have your account set up as to which. You may want to check those folders to see if they’re still there.

Backup methods for iPhone, iPad, and iPod touch - Apple Support -- Neither an iCloud backup nor computer backup includes any Apple mail data.

Hope that helps, and take care.