Search for email in Mail on iPhone
In the Mail app , you can search for emails using different criteria.

Search for text in an email
From a mailbox, swipe down to reveal the search field, tap it, then type the text you’re looking for.
Choose between searching all mailboxes or the current mailbox above the results list.
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.
Search by timeframe
Tap the search field of a mailbox list.
Enter a timeframe, like “September,” then tap
to see all emails from that timeframe.
To narrow the search, tap the search field again, then enter a keyword, like “meeting.”
Search by email attributes
In an inbox, tap the search field.
Before you begin typing, you may see suggested recent searches, recent documents, and links listed.
Enter your search criteria, then tap one of the listed items, or do any of the following:
Find all flagged emails: Enter “flag” in the search field, scroll down, then tap Flagged Messages below Other.
Find all unread emails: Enter “unread” in the search field, scroll down, then tap Unread Messages below Other.
Find all emails with attachments: Enter “attachment” in the search field, scroll down, then tap Messages with Attachments below Other.