Thunderbird.

You have to click in a cell to get the control handles. Click the arrow pointing up to add a row above, or down for adding a row below.

Click the circle with the x in it to delete the cell or row—you'll have to experiment to understand what this will do.

That's just it: password(s) used in Thunderbird, but Thunderbird itself has only the capability to remember a password, but it doesn't "have" a password itself.

When you change your password with your mail gateway/provider/whatever, you'll find Thunderbird will fail to log in the next time you launch or bounce it. It's at that point that you reveal the new password to Thunderbird and ask it to remember it. Also, this will typically happen twice per account since it provides for one password to receive mail for the account and another, separate once for the out-going server that sends mail. These two are potentially different depending on a couple of factors including your own choices.

This is inserted by Thunderbird when you copy and paste something into it from another application, like a browser or Word.

1. Select the text including the icon.
2. Choose Format → Remove Named Anchors.

First, it's impossible to recover addresses without being able to run Thunderbird. Without windowed access to the host on which your addresses reside, it's without hope. (So, access via ssh is impossible.)

Second, it's impossible to delete or place addresses in the default folders, Collected Addresse and Personal Address Book, inside the Thunderbird address book. In consequence, get used to naming the books you export and import something else and just not using those default folders anymore.

Next, you can only export one address book at a time. Begin by clicking on the address book to export first, then do Tools → Export... and do what's obvious (give a name, etc.).

To import, reverse the procedure by bringing up the new Thunderbird address book and doing Tools → Import....

This is ickier. First, there is an add-on to make it easier, however, it's unnecessarily burdensome. Just follow these steps at the command line, after installing and otherwise setting up Thunderbird on the new computer host:

1. Locate your Thunderbird data. This will in ~/.thunderbird/x, where x is a subdirectory with an automatically generated, discrete name like tig234sdf.
2. Down under that subdirectory, find one or more files (there will be one per e-mail account you've set up) named msgFilterRules.dat. These will be under separate subdirectories. For example, if you've got two Google mail-based accounts, likely you'll find them like this:

   ~/.thunderbird/tighs31a.default $ find . -name msgFilterRules.dat
   ./Mail/Local Folders/msgFilterRules.dat
   ./ImapMail/imap.googlemail.com/msgFilterRules.dat
   ./ImapMail/imap.googlemail-1.com/msgFilterRules.dat
   ./News/new.eclipse.org/msgFilterRules.dat
   

   where the first one corresponds to the first e-mail account you set up when you installed and configured Thunderbird. Etc.
3. Transfer that file to the new computer host locating the new subdirectory corresponding to the right e-mail account.

I did not find that I had to shut down Thunderbird on the new host before coping nor bounce it to see the rules once I'd copied them into place.

Enable menus in Thunderbird, then select View → Layout → Vertical View.

1. Position the cursor in the e-mail content.
2. Choose Insert → HTML...
3. Type or paste HTML into the space marked Enter HTML tags and text.
4. Click Insert.