I don't think you can. Alternatively try exporting in .ldif format and test whether Yahoo can read that.

I looked into IDIF but in Yahoo Mail there is no mention of it It is either csv or vcf. I found two field headers that needed to be changed - TB 'Primary Email' to Yahoo Mail 'Email' TB 'Home ZipCode' to Yahoo Mail 'Home ZIP' I got a lot of good help from Yahoo Mail Forums. It seems that it is not a 'problem' with either Yahoo Mail nor TB. Apparently most, maybe all, Email servers & Email clients have differences in field header names. First time around it was a big problem & very time-consuming to investigate & fix. But I learned a lot & now both Address Books are fully synced. It is not something that I need to frequently, & it will probably be a long time before I need to do it again. I have my paper notes to remind me how to it.

Thunderbird's own Import tool requires you to align the two sets of data. It's up to you to recognize what corresponds with what. There is nothing that demands that you change names, just identify congruent fields.

I'd presume that any system has its own way of accommodating these differences.

Importing is quite different from Exporting. I know all about 'align the two sets of data' from my initial Import (from Windows Live Mail), which was a time consuming exercise. But a one-time thing so it is not important. Exporting is quite different. In the procedures I've noted previously, first time around it is also a time consuming exercise. But after identifying the mismatched field header names, (in my case only two), it is easy to change the TB Export csv file in Excel. There are other advantages to modifying\saving the TB Export csv file in Excel - I can Delete the unused fields\columns. I create a file that is easy to copy to an external HD for extra Backup. I can print a paper file for even more Backup (even TB Help suggests that).

Overall I'm quite happy where I'm at now.

The export option to a csv file does not show up for my address book so I can not export it. However another thunderbird user on this computer has the option export show up for the address book. I can not figure out what is different about the two thunderbird setups.

Right at the end of the export sequence you are asked for a filename and a location to save the exported data. It is at this point, in the "Save As" dialogue, where you use the pull-down to select CSV rather than LDIF

I can export the address book on another user of this computer's thunderbird but not on mine. I did not have any luck attaching screen shots so here are words for the dropdown menus.

when I click tools on the other user's thunderbird I have a dropdown that says Mail & Newsgroups Import Export Options

On my thunderbird the tools dropdown says Address Book Saved Files Add-ons Activity Manager Chat status Join chat Message Filters Run Filters on Folder run Junk Mail Controls on Folder Delete Mail Marked a s Junk in Folder Import Error Console Allow Remote Debugging Clear Recent History Account Settings Options

So I do not have an export. Figure there must be some difference in way two thunderbirds are setup but can't find what to change.

Thanks for any help.