Contacts from gmail are not automatically imported
In eM client, contacts were automatically imported from Gmail, making the transition seamless and painless. I had to manually export the csv file (from eM client) and import it into Thunderbird so I can send an email. Why isn't it possible when all the emails are there? The software should just copy all the emails and put it into the contacts.
Opaite Mbohovái (1)
If you are still using Google Contacts I'd suggest using a Thunderbird add-on to synchronize Thunderbird's address book to Google Contacts.
https://addons.mozilla.org/en-GB/thunderbird/addon/gcontactsync/ works for me.
Thunderbird has import tools for a few selected email clients. Right now, I guess eM client isn't one of them. It's hard to tell what Thunderbird does support because it silently searches for known compatible data sets. If I don't have eM client installed, I have no data set for it to look for, so I can't tell for sure if it could be imported.
Did you "import" your email messages, or were they on IMAP-connected servers?