Please read this to learn the difference between IMAP vs POP: http://www.pop2imap.com/ POP is the old style that just downloads e-mail from the Inbox to your computer. IMAP is the new style which shows you the contents of all the folders on the server. Dealing with Spam is different for the two types. With POP, you have to log into webmail to see what the e-mail provider has put into it's spam folder, while with IMAP, Thunderbird will show you that folder and it's contents.

An e-mail account in Thunderbird is set up as either IMAP or POP. It cannot be changed later. Only deleted, then re-created as the other type.

1) Using one set of folders (Inbox, Sent, custom folders, etc.), to hold the e-mail for multiple accounts/e-mail addresses.

This is easiest done when setting up an e-mail account using POP. It can also be done when using IMAP, but you have to set up message filters to automatically move incoming e-mails to a central Inbox.

For POP, once the account is set up:

Right-click your account in the normal folder view of Thunderbird and choose Settings, then choose Server Settings for the account on the left side. You will see options like my first screenshot below. Click the Advanced button I have indicated.

Change the settings in the window that comes up to match my second screenshot below.

Then click OK on everything, close Thunderbird, then start it again.

Once these options are set for each POP account, all your e-mails from all accounts will go to the Inbox in Thunderbird's Local Folders.

For IMAP, once the account is set up:

You set up a message filter for each IMAP account to Match all messages, and Move Message to Inbox on Local Folders.

Then you change the settings for Copies & Folders for the account (Right-click your account in the normal folder view of Thunderbird and choose Settings, then choose Copies & Folders), so Sent, Archives, Drafts, and Templates are saved under Local Folders, instead in the IMAP account.

You would still see the IMAP folders for the account, but you can collapse them down so you just see the e-mail address. You would need to check the IMAP Spam folder for what is in there, but that will be easier than with POP, where you have to log into webmail to see that folder.

2) "It looks like all current email messages will download from Gmail, and I do not want that. Is there a way to only have new emails download?"

When using IMAP, you see the entire contents of the Inbox (and other folders), as they are on the server. New e-mail messages will show.

When using POP and if you leave messages on the server, the very first time Thunderbird checks for messages for an account, it will download all the messages. After that, Thunderbird will only download the new ones it has not already downloaded before.

3a) "I have a bunch of email filters set up - will the downloaded messages use those, or do I have to go with the Gmail tags created folders?"

Thunderbird filters will work the same for Gmail accounts as with any other type of e-mail account. Gmail tags will not play any role in this.

In Thunderbird, each e-mail account has its own set of message filters. So you will have to copy the filters from your current Verizon account(s) to your new Gmail accounts. This can be done using the add-on quickFilters which allows the ability to copy filters from one account to another. You can select all the filters, copy them, then paste them into the filter list for the other account. See Installing an Add-on in Thunderbird.

3b) "I have two Gmail addresses, will the two sets of messages be stored separately or will it create two sets of folders"

This goes back to your question 1), which I have answered.

4) "Will a default be created now, and can I delete the identity that is currently acting as default?"

You can set up any number of different e-mail address in Thunderbird, receiving, sending all of them at the same time. Each e-mail address is set up as an "Account" in Thunderbird. I believe that is what you mean by "identities". You have have your Verizon accounts and Gmail accounts in Thunderbird at the same time.

In Account Settings, one e-mail account is set up to be the default first choice to send an e-mail from, but you can easily switch the "From" line in the compose e-mail window to be for one of the other e-mail addresses.

5) "Any other tips or gotchas that I should watch out for?"

Make sure that you move all your Verizon e-mails to Thunderbird's Local Folders before you remove the Verizon account(s) from Thunderbird. Otherwise you will lose them all when you remove the Verizon accounts.

You will need to create two separate Gmail addresses for what you are calling your two "identities". The two will be completely separate from each other, and each will be set up separately in Thunderbird as accounts.

The third screenshot below shows the correct settings for Gmail POP when setting up the account in Thunderbird. The forth screenshot shows the same settings for Gmail IMAP.

Hi Bruce!

Thanks so much for this comprehensive answer! I will need to read it a couple of times to fully digest it, and then probably will experiment a little. I did find out that when you use IMAP, if you want to save a message you can move it to a folder outside the Gmail account, and then it is deleted from the server but not from Thunderbird.

The one thing that is is different in my Thunderbird is that my local folders are all empty. Each account - I have two for the two Verizon addresses, feed into all the folders that are listed under the original email identity. Again, please forgive my terminology is wrong.

When I go into account settings, my two Verizon email addresses each have separate accounts, but when I look at the list of Thunderbird folders that contain the messages, there is only one set of folders and both email addresses are fed through the filters. Then at the bottom are the local folders - empty. I think this must be due to that global setting I used when setting this up years ago. So long, I don't remember exactly what I did. 8-(

I did play around with a Gmail IMAP set up, and it created a new account called p...@gmail.com. All messages on the server are there. I think I now understand what I read online about the messages not downloading until you click on them.

It is not clear if I will be able to do what I wanted to achieve - but I need to re-read what you wrote before jumping to that conclusion. In the IMAP Gmail account, the messages are in different folders based on the tags from the Gmail account. So, that is already defeating what I want to do.

Anyway, thank you again for all this great information!

Hi again Bruce! I tried last night to use the POP instructions for linking a gmail account and it told me the password was wrong. I know it was right, and entered it again anyway, but still no success. Using IMAP worked fine. Do you have any suggestions on how to troubleshoot the POP functionality?

Thanks for any help!

Regarding POP. Logon to the gmail webmail account via browser, have you selected the 'Pop' option ? Pop needs to be selected. Have you selected the option to use 'less secure apps' ? You need to select to use 'less secure apps'. https://support.google.com/accounts/answer/6010255?hl=en

Thanks toad-Hall! I did have POP enabled, but did not have the "less secure apps" turned on. Interestingly enough, I got an email from Gmail that just showed up - hours after the denial of access - telling me the same thing. But, now I am not so sure I want to go this way after reading all the warnings. sigh! But, at least the mystery is solved! Thanks so much!