python imaplib - mark email as unread or unseen

Question

Searching here and on the internet, there are a lot of examples to how to mark a message as SEEN, even though this is automatic with imap.

But how can I mark an email as UNSEEN or UNREAD.

I have a script in python which receives UNSEEN messages, and it works great. But after reading them, imap automatically marks them as SEEN which works fine but only if the script has no errors, because if it raises an exception, I want the email to be marked again as UNSEEN, so next time the script will read that message again.

How can I achieved this?

I have also used mail.select(mail_label,readonly=True), but it doesn't help because with that I cannot mark a message as SEEN which I also need. I also want this to work with Gmail.

Answer 1

You can easily clear the \Seen flags with this command:

tag UID STORE -FLAGS (\Seen)

but your software will probably be more robost if you only set the \Seen flag in the first place after you have successfully processed a message. That way, if anything goes wrong while you are processing a message (even if the connection to the IMAP server is broken) the flag remains unset and you can retry that message the next time the script runs. You do this by avoiding the IMAP server's automatic setting of the \Seen flag by using BODY.PEEK instead of BODY.

In Python, I think that STORE command should be issued like this but I haven't tried it.

connection.uid('STORE', '-FLAGS', '(\Seen)')

Answer 2

In Python, the imaplib module describes STORE as:

(typ, [data]) = <instance>.store(message_set, command, flags)

so, the following line will let you set the message to READ ('+FLAGS') or UNREAD ('-FLAGS') as required.

connection.uid('STORE', MESSAGE_ID, '+FLAGS', '\SEEN')

As you see, the secrets is on the FLAGS command ;)