Import address list from text file
If you have a list of email addresses stored in a text file, you should be able to import these addresses easily into a Thunderbird address book by doing as described in this thread. Additional hint: The import utility accepts only commas (",") as separators for csv, not semicolons (";").
Importing contacts from a text file works best if the data is organized into same number of fields (columns) as Thunderbird will import and that the fields are in the same order as Thunderbird's import order. You can rearrange prior to import through the import utility, but it is not a quick process.
The import attributes are, in order:
First Name, Last Name, Display Name, Nickname, Primary Email, Secondary Email, Screen Name, Work Phone, Home Phone, Fax Number, Pager Number, Mobile Number, Home Address, Home Address2, Home City, Home State, Home Zipcode, Home Country, Work Address, Work Address2, Work City, Work State, Work Zip, Work Country, Job Title, Department, Organization, Web Page 1, Web Page 2, Birth Year, Birth Month, Birth Day, Custom 1, Custom 2, Custom 3, Custom 4, Notes