Imap_ssl.search one letter name

[Linh_Lee]

resp_code, mails = imap_ssl.search(None, '(FROM "a")')

I want to search emails from a specific one letter named user, "a".
Example:

<(e-mail address removed)>
<(e-mail address removed)>

Problem is, search results cause all users with an "a" as part of there name to be returned.
Example:

(e-mail address removed)
(e-mail address removed)

Any way to isolate the search to one letter name?