What I would like is to see is aliases handled much like identities in Thunderbird.
In eM Client, sending from an alias simply changes the reply to address (return-path) in the email header, not the mail from address. So receiving an email sent from an alias does not appear to come from the alias, but the parent account.
In Thunderbird, identities have the option for setting different SMTP accounts to the parent, so an email sent from an identity has the identity email address as both the from and the reply to address.
Of course what you can do, and what I have done, is to setup so many SMTP only accounts in eM Client to handle this. And because you can’t setup a SMTP only account, you have to setup IMAP/POP and then disable the IMAP/POP section leaving just the SMTP. Takes a lot more time to do it in eM Client this way, than setting up identities in Thunderbird. And for those on free accounts - sorry but the 2 account limit makes this method beyond reach.