Thunderbird saves "collected" email address from emails I receive. Does Em Client have this feature?

Collected email addresses

If you mean that you wish to save an email address to your Contacts list, you can do this by:

  1. Highlight “From…” address at top of email
  2. Click on “Add to Contacts”

Hello Mike,
this cannot be set automatically for Senders’ addresses, but it’s just as Norman above suggest - you can right-click the Sender in the header and ‘Add to Contacts’ from there.