Late last year I had absolute nightmare with my email accounts after I messed up my web-host migration. The long and the short of this is that I lost a lot of emails, and a lot of the contacts associated with those emails, too. We back up our machines regularly, be it PC, Mac, iDevice or Android, but we're not always so contentious about our individual pieces of software and their contextual data.
It's always worth exporting your contacts and backing up emails. It's a quick job that'll save your bacon down the line.
Exporting Outlook Contacts
Head to File>Open & Export>Import/Export. In the dialogue box select Export to a File, followed by Comma Separated Values. The next screen allows you to scroll through your folders. Locate your Contacts folder, and enter a memorable name for your exported CSV file.

You can click through the next field if you want, or alter the Custom Field settings. Fields are the name given to variables in your contacts list. If you want to export only a limited set of field parameters, press Clear Field. You can then add another set of fields. The image below gives you some useful business listings for your CSV file – you could then delete any listings in the CSV file without those matched parameters, but that's another story.

Outlook also features two other export file formats:
- Outlook Data File - .pst: A data file containing messages and other data that can be stored on your computer. Email messages and other important data is downloaded and stored, or mail can be archived in chunks to a single .pst file. Exporting or archiving your email can provide more space on your mail server, is this is an issue. Most commonly used by POP3 accounts.
- Offline Outlook Data File - .ost: Most other email account types will export their messages and important data to a .ost file, including Microsoft Exchange, Outlook, Google Gmail, and IMAP accounts. Your vital information has been delivered too and saved on the mail server, whilst a synchronised copy is stored on your machine.
I'd never considered backing up my email archive before my webhosting debacle; now it's once every other month, just to be sure. For those of you with limited mail server space, saving and deleting can free up some valuable bytes.
Importing Outlook Contacts
Importing contacts to Outlook is also a seamless task. Head back to File>Open & Export>Import/Export. You can import from a VCard, a .csv, a .txt, or a .pst, amongst others. Select Import from another program or file, followed by the file type of your choice. I'll be using a .csv. The import wizard can then replace duplicates, or allow them to be replaced with the incoming contacts, or simply ignore the duplicates. Select the option correct for you.

Locate the contacts file you'll be importing. The next screen asks for the destination folder. You should browse the available folders until you find Contacts. Select this, and press next. You'll note the options to change the import fields, just as we could edit them when exporting our contacts. This time around we'll stick with the default.
Exporting Gmail Contacts
Gmail contacts are less of an issue as they are maintained online. Still, it's always handy to unify your contacts list between fragmented half conversations across multiple clients.
Sign into the Gmail account you'd like to export. Click the word Gmail in the top left corner, then Contacts. You'll be whisked away to a new screen containing all your contacts from your Gmail, and potentially from your Android phonebook too, if that's your preferred device. Select More to open the drop down menu – you should now see an option to Export your contacts.

The dialogue box provides a number of selection options. You can export your entire contacts list, your starred contacts, your Google Circles contacts, or a list of your most frequently contacted. You can also build a custom contact list for export within Gmail by adding each record to a separate contact list. Do this by selecting each record, then heading to the contact options bar. You should be able to add them to a single group.

Once you're ready, select your export format. Unless your contacts are moving from one Google account to another, or you're export to an Apple product, select the Outlook CSV format option. This uses a standardised format that you'll be able to use with the majority of email clients. Save, and you're done!
Importing Gmail Contacts
This process is very similar to export, except you show Gmail the file you want to import. Once inside the Gmail Contacts page, head for the same More button we pressed earlier, but this time select Import. You'll be met with this dialogue box:

Once you've select your file, press Import.
Exporting Thunderbird Contacts
Open the Address Book, situated on the top toolbar. Once open head to Tools>Export. This will bring up the Save As dialogue box. Thunderbird can export to .csv, .ldif, and .tab/.txt.

I would choose either .csv, or .tab/.txt for your Thunderbird contact export, especially if migrating to Outlook. .ldif is supported by both Mozilla Thunderbird and Apple Address Books, but not Outlook. If you do come across a .ldif file type, or you do not have any software installed that can open it, a .ldif file can be converted into a .csv using freely searchable software.
Importing Thunderbird Contacts
To import contacts into Thunderbird select Import instead of export, and follow the onscreen dialogue options – you can't really go wrong!
Voilà. Your address book should now be bursting with your loved ones and business associates.
Hope you'll now feel confident importing and exporting contacts using Outlook, Gmail, and Thunderbird – but realistically, most import/export features are relatively universal across most email clients. Good luck!
Have we helped? What email client do you use? Let us know below!