Bug #48117 for Net-Server-Mail: Thunderbird abborts on any 'MAIL FROM:' reply from Net::Server::Mail::ESMTP

I hope this problem can be reproduced by you, as it is quite dificult to find out what could be wrong here. When writing a simple smtp server using Net::Server::Mail::ESMTP (with , the mail client thunderbird aborts directly after receiving a reply from 'MAIL FROM'. This may be relevant config stuff: $smtp->register('Net::Server::Mail::ESMTP::PIPELINING'); $smtp->register('Net::Server::Mail::ESMTP::8BITMIME'); $smtp->register('Net::Server::Mail::ESMTP::SIZE'); $smtp->set_size($maxmessagesize); After I return the 250 reply from the MAIL FROM callback, I get a disconnect on the server side, and an error message telling me no connection could be made on the client side. Looking at it with pcap it is clear that the client does the disconnect. I can find no reason why Thunderbird should disconnect and throw an error, but as Thunderbird seems to work perfectly with the same setup sending to postfix, it appears to be a Net::Server::Mail problem. I hope this is sufficient information for you to reproduce the problem. If it is not, please let me know if I can be of any help solving this. Rob