Couldn't find a reasonable py3 gmail package, and I hate using Google's APIs when I don't have to, so here we are. This only reads emails currently. I have no need to send emails but if there's a decent PR, I'll take it.
Criteria Parameters
ALL - return all messages matching the rest of the criteria
ANSWERED - match messages with the \ANSWERED flag set
BCC "string" - match messages with "string" in the Bcc: field
BEFORE "date" - match messages with Date: before "date"
BODY "string" - match messages with "string" in the body of the message
CC "string" - match messages with "string" in the Cc: field
DELETED - match deleted messages
FLAGGED - match messages with the \FLAGGED (sometimes referred to as Important or Urgent) flag set
FROM "string" - match messages with "string" in the From: field
KEYWORD "string" - match messages with "string" as a keyword
NEW - match new messages
OLD - match old messages
ON "date" - match messages with Date: matching "date"
RECENT - match messages with the \RECENT flag set
SEEN - match messages that have been read (the \SEEN flag is set)
SINCE "date" - match messages with Date: after "date"
SUBJECT "string" - match messages with "string" in the Subject:
TEXT "string" - match messages with text "string"
TO "string" - match messages with "string" in the To:
UNANSWERED - match messages that have not been answered
UNDELETED - match messages that are not deleted
UNFLAGGED - match messages that are not flagged
UNKEYWORD "string" - match messages that do not have the keyword "string"
UNSEEN - match messages which have not been read yet