I'm following these official Google steps on checking one Google inbox from another without forwarding the mails: https://support.google.com/mail/answer/21289?hl=en
I've done everything it says, but I'm hitting some strange errors which seem to suggest Google is blocking Google from linking with itself like this when I fill in the popup page that appears from:
Settings > Accounts and Import > Check email from other accounts: Add a mail account you own
If I use POP3, which is enabled in both Gmail accounts, on pop.gmail.com and port 995, I get this error:
Server denied POP3 access for the given username and password. Server returned error: "[AUTH] Web login required: https://support.google.com/mail/answer/78754"
I'm logged in to both accounts. The linked page isn't relevant to the problem, it's just a generic help page for regular web log in offering advice such as "make sure you’re using the right password" (I definitely am, I get a different error if I intentionally use the wrong password). This suggests that Google doesn't recognise this method of accessing the account.
Also, I get an email "Someone has your password" warning me that an unrecognised device in the United States (i.e. Google's server...) has tried to access my account.
If I use IMAP, which is also enabled in both Gmail accounts, on imap.gmail.com and port 993, I get this error:
There was a problem connecting to imap.gmail.com
Server returned error: "Missing +OK response upon connecting to the server: * OK Gimap ready for requests from [some address]
It seems like Google is blocking access to itself. But access is allowed on both accounts:
- For POP3, it's set to "1. Status: POP is enabled for all emails"
- For IMAP, it's set to "Status: IMAP is enabled"
I found a thread where someone suggests they had the same problem with IMAP and fixed it by unticking the box "Leave a copy of retrieved message on the server", but I have the problem regardless of this setting.
Is there something special I need to do beyond Google's instructions to allow Google to talk to itself?
Update: curiously, my latest email warning (I'm not sure if it's regarding POP or IMAP) says this:
Google will continue to block sign-in attempts from the app that you're using because it has known security problems or is out of date.
Not sure if it's talking about the Gmail feature, or POP or IMAP in general.
I've removed other links between the accounts e.g. delegate access, and I've also tried this from a google groups comment using two different browsers https://productforums.google.com/forum/#!topic/gmail/uBdBQAuGeTw:
...Account B (the one getting added to Account A) is blocking Account A, preventing a successful login.
What worked for me is logging into Account A with Firefox, then logging into Account B with IE. From Account B I visited this page: https://accounts.google.com/DisplayUnlockCaptcha and followed instructions, clearing the Captcha. Once done, adding Account B to Account A immediately worked.
The same thing still happens.