Well you will not consider the answer a joke. No! you can not do it your way. Not that I have the foggiest idea what a "*hit-simple" is. I think you are trying to say if you get email from to an email address, Thunderbird should somehow work out it is not spam and add an account for this email address. It could do that, and staret an account add process if mail comes into an To: that is not already defined. But what happens with mail send BCC, the to is just some random address. Sometimes the address belongs to the sender, sometime is it just a fake and other times it is the words "undisclosed recipients" but it is not as simply as having the software add folders for each new to: address it sees. There are some add-ons that already address some of your points. At least I think they do from my limited understanding of your comments. Have look here https://addons.thunderbird.net/en-US/thunderbird/search/?q=quick+filter&appver=&platform= The email landscape is however changing, so if an email from curly@stooges.com arrives with most providers these days they check DKIM, SPF and DMARC. Most also do reverse DNS queries to determine if the originating server is registered in the domains DNS as an approved sender for the domain part of the email address. So I have no idea where your single SMTP server is located, but sending mail for your example curly@stooges.com will require the domain you are sending from to be in the stooges.com DNS entry as an approved sender. So if your single SMTP server is with a big provider like an ISP where you have no control over the DNS record, your days of sending from a single SMTP are about done already. Most providers will simply drop the email and not deliver them.