"Authentication error" backing up Yahoo email to gmail

You signing out of your accounts should have not effect on gmail pulling your email into their inbox.  For the att/yahoo account in question can you log into it without any problems?  If so, and you are still getting errors from gmail, then I believe you set the email address or password incorrectly so recheck it.

You set this stuff up in gmail's settings, "Accounts & Import".  But are you trying to do their "Import mail and contacts" or "Check mail from other accounts"?  If I recall I think one (or both) of them is going to cause that att/yahoo email account to put up a dialog asking you to give permission for gmail to access it the first time.  So you really should be logged into the att/yahoo account when you do this initially to give that permission.  If gmail doesn't get the acknowledgement it's going to error out.

Note, these kind of accesses are done as if gmail was a email client app configured as POP and as such will see only see the target inbox since that is all a POP client can access.  I never tried either of those "Accounts & Import" options in gmail so I don't know if it asks you to access as IMAP or not as an option.  If it does then it would fetch all the target mailboxes and create those mailboxes in your gmail account, not just copy over the inbox contents as a POP client.

"For the att/yahoo account in question can you log into it without any problems?" Yes, I can log into my mail from Windows/Chrome/AT&T - Yahoo and also from the Yahoo app on a Samsung phone, both before and after getting the subject error.

"If so, and you are still getting errors from gmail, then I believe you set the email address or password incorrectly so recheck it." In my attempts to get around this, I have tried to initiate the backup maybe 15 times. The way Google Import Mail and Contacts works is that it asks the user to independently login to Yahoo first rather than providing those credentials to gmail. So there is absolute confirmation of a successful login to Yahoo mail. 

You set this stuff up in gmail's settings, "Accounts & Import". Yes.

But are you trying to do their "Import mail and contacts" or "Check mail from other accounts? Import mail and contacts.

If I recall I think one (or both) of them is going to cause that att/yahoo email account to put up a dialog asking you to give permission for gmail to access it the first time. No, as stated above, the gmail dialog asks the user to login to Yahoo independently before proceeding. As an aside, I successfully used this process a couple of days ago to back up another Yahoo email account.

So you really should be logged into the att/yahoo account when you do this initially to give that permission.  Yes, and I am.

I never tried either of those "Accounts & Import" options in gmail so I don't know if it asks you to access as IMAP or not as an option. No option is given for POP vs IMAP. No mention is made of either in the error message. I looked for the option to enable POP on the Yahoo side, but apparently that option has been taken away. I assume POP and IMAP are always enabled. For what I'm trying to do - backup my mail - POP should be fine. (Not that I don't fear that AT&T would loose it - actually that's exactly why I'm backing it up.)

Here's a thought. The backup I started for another email address on my account a couple of days ago is still running. Do you think that would cause the Yahoo server to deny access credentials until the first backup completes? Same account - two different email addresses/ inboxes, etc. Any way to check on that?

I really appreciate your help!

Alan

If gmail doesn't allow you to specify these functions as POP or IMAP then it is is using POP.  It's just acting like email client app configured as POP. 

You shouldn't have to tell the att/yahoo webmail whether it's being access as by a POP or IMAP client so no setting is needed.  But there is an option to pass any received spam to the POP client.  You didn't see it since it's only shown in the classic (basic) email layout (gear settings -> more settings -> switch to classic mail, but this is off topic so forget about it).

Here's a thought. The backup I started for another email address on my account a couple of days ago is still running. Do you think that would cause the Yahoo server to deny access credentials until the first backup completes? Same account - two different email addresses/ inboxes, etc. Any way to check on that?

Days?    I don't think two different "clients" accessing at the same time should be a problem.  But of course with yahoo anything is possible!  I do know I can access my att/yahoo email from my Thunderbird client while the webmail is showing at the same time.

It sounds like you are doing everything correctly so I don't know what the problem may be.  I guess I would experiment using a secure mail key in place of the password you give to gmail as the next experiment. Or am I a little confused in that you say you log into to your yahoo account and then when you start the gmail fetch no dialog appears in the yahoo webmail to allow gmail to access the yahoo account?  I am not saying that's wrong.  Just curious because I'm pretty sure "Check mail from other accounts" needs permission from the target account if "Check mail from other accounts" does what I think it does (i.e., link accounts so you can use the linked account directly from, in this case, gmail instead of explicitly using the linked account).  I know yahoo put up an "allow" dialog for me when I linked it to my primary email account (not att/yahoo or gmail).

"Or am I a little confused in that you say you log into to your yahoo account and then when you start the gmail fetch no dialog appears in the yahoo webmail to allow gmail to access the yahoo account?" It seems to work either way. If I log into Yahoo first and then start the fetch from gmail, I get no prompt to log in - it goes directly to the "authorization failed: message. But if I start the fetch without first logging in, a Yahoo login dialog is presented - which explains what you are remembering. Another observation I just remembered - each attempt to start a fetch results in an email being placed in my Yahoo inbox stating "Your Yahoo account [email address] was just used to sign in on ShuttleCloud Migration. If you did this, then you're all set."  It's a security check. ShuttleCloud Migration is the intermediary Google uses to effect the transfer. So apparently all the parts are getting connected, but authorization fails. Good suggestion to try logging in to gmail with a secure mail key. I'll give that a try tomorrow. I think security is making our lives difficult - but we can't live without it.

Thanks again! Alan

Just googled "ShuttleCloud Migration".  Nothing like having more fingers in the pie.  I suspect it's somehow the cause of all this (and probably your other transfer taking days as well too) and I don't have a solution.  But I suggest you look at some of the search results in that google search.  Maybe you can find a solution.

If you can't figure this out, get tired of waiting for that other transfer to finish, give up on letting gmail "doing you a favor" and just do the transfer yourself!    Set up an email client (pick your favorite - if you don't have one Thunderbird and Outlook are two popular clients), configure two IMAP accounts in it, one for your yahoo account and one for your gmail account.  Once the yahoo IMAP account is set up it will get populated with all the folders (not just the inbox) from your yahoo account.  After that is done, in the client copy all the folders (or contents for the predefined folders like inbox) to the gmail account in your email client.  That will populate the corresponding folders on gmail.  The time for all this may still take a while depending on the number of emails in those folders.  But at least in are mostly in control of these transfer and not dpending on some mysterious 3rd party transfer agent.

Of course after you do this process you may like using the email client all the time instead of the webmail.

If you decide to take this approach here's a page on how to configure some email clients for yahoo.  Gmail would be about the same except for the sever info.  For IMAP that can be found here.

I like your suggestion to do the transfer myself with Outlook. I have Outlook 2010 installed for calendar, but never set up email, and haven't had a need to upgrade Outlook. That may also afford a third copy of my mail for greater backup reliability. I'm assuming Outlook will store all IMAP all email locally but I need to verify that for Outlook 2010. "Control" is the magic word you used - we can rarely have too much. And yes, I may very well like Outlook better than webmail.

Thanks again for all your help! I'll report on my results.

I'm assuming Outlook will store all IMAP all email locally but I need to verify that for Outlook 2010.

By definition, if an email client supports IMAP then the stuff is "in" the IMAP client(s).  All IMAP clients are kept in sync by the server (which is always mirrored in the webmail).  What happens to one, happens to all.  So the technique I described is using that feature to effect the transfer.  Account A server syncs with client, you manually copy the stuff  to client's account B, and B syncs with its server B.  End result, client account A is in sync with server A, client account B is in sync with server B.  A and B are totally independent except for the fact they just happen to have the same stuff on them initially since that's how you created B.  Your client has both copies. 

If now you decide you no longer want to use IMAP in the clients you can create a POP account in the client C (presumably set up for account B) and again copy those folders (or folder contents) from either A or B to C within the client.  Finally disable IMAP accounts A and B. Result is now you are accessing server B with POP client account C and you can delete A and B in the client so long as you disabled both of them first.  If you delete them while still enabled you will delete the stuff on the server!

Note there is no way to convert an IMAP account to a POP account (or vice versa) in the client (all the clients I know of that is) so that's the reason you need to create the separate POP account.