It seems Yahoo! Mail no longer requires the custom command (GUID 1), now you can access your Yahoo! Mail via IMAP using the settings below:
Yahoo! Mail IMAP Settings
Configure Yahoo imap with the following servers:
imap.mail.yahoo.com port 993 (SSL/TLS) smtp.mail.yahoo.com port 465 (SSL/TLS)
android.imap.mail.yahoo.com port 993 (SSL/TLS) android.smtp.mail.yahoo.com port 465 (SSL/TLS)
Yahoo! Mail IMAP "Hacks" - Background info
In the past there have been several "hacks" to enable IMAP access for Yahoo Mail, some of which included:
- access it from your mobile device
- use a special hacked version of Thunderbird or Mutt which sent GUID 1 header
- use a proxy app such as ypop
Here is a quote from wikipedia:
It is possible to get direct IMAP access. Yahoo! operates IMAP and secure IMAP servers (imap.mail.yahoo.com in particular), which are globally accessible. However they require a specific, non-standard IMAP command to be sent before login is done, namely: “ID ("GUID" "1")”. It is feasible to modify an open-source email client to send the ID command, and there are modified versions of Mutt and Mozilla Thunderbird available to download. Alternatively, you can connect an unmodified email client through an IMAP proxy that adds the ID command. A commercial software package that accomplishes this is called 'Yahoo IMAP Connector', available here.
It is also possible to send mail through mail clients as Yahoo! also operates an SMTP server (smtp.mail.yahoo.com). It is necessary to enable SSL through port 465. For IMAP and SMTPs access the username is the user's Yahoo! Mail address and the password is the same as for webmail access.