Yahoo Mail issues and solutions (error -11 and OAuth2)

May 9, 2018

Update (May 17): A fix is now available for the Yahoo -11 error.  The fix is labeled as POP Peeper v4.5.1.  It is currently in the test (pre-release) phase and if there are no reported issues, it will be released officially soon.  See this page for more information.  Original content follows —


Right now, there are 2 issues with Yahoo that have been affecting POP Peeper.  One is with WebMail (error -11) and the other is with IMAP (OAuth2, specifically).  I will quickly explain the problems and solutions and then go into details (in case Yahoo is listening).

WebMail: Error -11
This is a symptom of an issue that I expect Yahoo will fix (details below).  I have fixed the problem in POP Peeper, but the problem is that this will require a full update to POP Peeper and not just the WebMail plugin.  This may yet be necessary if Yahoo doesn’t fix the problem soon.

Solution: Switch to IMAP
Edit the account in POP Peeper and change the “server type” to “IMAP.”  Optionally, press the OAuth2 button that will appear to the right of your login name, as this is more secure (but if you run into problems, see the next section).

Alternatively, you can wait it out (whether that’s Yahoo fixing it on their side or if I decide it’s taking them too long and a POP Peeper release is necessary).  However, using IMAP is recommended over WebMail regardless, so you may well take this opportunity to switch.

IMAP: OAuth2 empty page

If, during the OAuth2 process, you see a page like the image on the right, you have 2 choices:
1) Simply press the ‘X’ button on the top-right (next to “Yahoo!”, not the ‘X’ in the title bar) and continue with the OAuth2 process

2) Log into your Yahoo account with your webbrowser, log out and sign back in and accept the TOS.  Then, return to POP Peeper and re-do the OAuth2 (close the existing OAuth2 window)



For the webmail issue, the reason that this is occurring is because some of the http headers that Yahoo is sending are excessively large — I’ve seen headers ranging from 14KB to 28KB.  I have confirmed that these same headers occur when logging into Yahoo Mail using a webbrowser (Internet Explorer 11, specifically; because it still has one of the better network profiling tools).  Here is a sample of the header

Content-Security-Policy-Report-Only: child-src ‘self’

This goes on and on, then has a few other URLs and then another long block of a different google URL.  Yahoo should fix this as it doesn’t seem to serve any purpose; unfortunately, POP Peeper wasn’t designed to handle this size of header and so it loses some important data (this will be fixed in any post-v4.5.0 releases).  Further, this issue seems to come and go; it may work for hours at a time, and then fail.

The empty OAuth2 page seems to be connected to the new TOS that Yahoo is requiring.  That’s about all I can tell you about this issue, but hopefully Yahoo will clear this up soon, too.


Yahoo IMAP issue

February 17, 2018

Update: Yahoo has fixed the problem.

Yahoo’s IMAP server is currently reporting the following error:

This is a server-side error and it affects all IMAP clients. They are aware of the issue:

In the meantime, you can consider switching POP Peeper to access your account using POP3 or WebMail (edit the account and change the ‘server type’ to ‘POP3’ or ‘Yahoo’) but be aware that POP Peeper will need to download all existing email in your inbox whenever you change the protocol. If you had been using OAuth2, be sure to enter your password when accessing with POP3 or WebMail.

You can track the issue here:


AOL/AIM error in POP Peeper (fix available)

January 19, 2018

Update (Jan 20): AOL has discovered the problem and fixed it on their end, so this patch is no longer necessary.  However, this change will be included in future versions of POP Peeper in case it ever happens again (with any IMAP service).

Today, AOL/AIM accounts that use IMAP have started reporting an error in POP Peeper, typically a “time out” error.  The reason for this is because a response from the aol server includes an invalid null character and this prevented POP Peeper from parsing the response correctly.  A patch is available for download so that you can get your aol and aim accounts working properly again.  Most likely, a full update (POP Peeper v4.5.1) will occur soon in response to this issue (and will address a couple of other issues, as well).


  1. Download the patch
  2. Exit POP Peeper
  3. Open the zip file you downloaded in step #1 and copy Imap.dll to the folder where you have installed POP Peeper.  This is typically:
    C:\Program Files (x86)\POP Peeper\
  4. Restart POP Peeper
  5. Test your AOL/AIM accounts
  6. If you still have an issue, make sure that you applied the patch correctly:
    • From the main menu, select Help / About
    • Find “IMAP” in the list and the ‘Current’ column should be:

POP Peeper v5 more details

December 12, 2017

Yesterday, I posted a screenshot that showed 2 features:






The “obvious” one is the capability to search your inboxes.  This will be an indexed search on the local messages which means that it will return results very quickly.  This is one of the biggest features that will be added in v5 so you can expect more information about this before the release.

The other feature is hidden in the Accounts List, on the left.  If you had the same accounts in POP Peeper v4, the order would be: Local01, Local02, etc.  v5 adds the ability to re-order the accounts simply via drag & drop.  No more having to rename your accounts to get the order you want!

More features will be announced after the new year.  Are you happy to see these features?  Let me know what you’d most like to see added to POP Peeper.


POP Peeper v5 Sneak Peep

December 11, 2017

Now that POP Peeper v4.5 is out, v5.0 is on the horizon.  I’m usually tight-lipped about what features will make it into the next version until the features have a “better-than-not” chance of actually making it in (some features may be more complicated than anticipated and it’s better to delay them for another version rather than delay the release), but with v5 well under way, I’ll start releasing some information about what you can expect.

In this first preview, two of the most requested features are shown — can you spot them?  One should be very obvious, the other is more subtle.  I’ll provide more details tomorrow.

Click the thumbnail for full-screen image.