Hello,
I recently switched to Fedora 43 (Gnome) from Debian 13.
Daily user of Thunderbird, version 146.0.1 from Fedora’s RPM package.
Since then, I’ve noticed extreme slowness in Thunderbird :
- sending an email can take up to several dozens of seconds : the progress window keeps showing “sending message” for a very long time sometimes,
- fetching emails : it’s a lot less reactive updating IMAP folders than previously (i.e. with Debian).
While sending an email, running a packet capture with Wireshark reveals an issue during TLS negociation with the SMTP server (Postfix on Debian). There can be up to 30 seconds between the “Server Hello” message and the “Change Cipher/Application Data” message from the client (Thunderbird).
Which makes me incrimate Thunderbird, more than the server. Especially since the change occured on the client side (Debian => Fedora) and I face no issue on other clients such as K-9 Mail on an Android phone.
In this screenshot from the packet capture, frame 7 is sent by the SMTP server. It’s immediately acknowledged (from a TCP standpoint) by the client (Thunderbird) in frame 8. Then 20 seconds later, the client goes on with the TLS negociation.
The behavior is similar when I force Thunderbird to use IPv4 by setting network.dns.disableIPv6 to ‘true’.
Does anyone have a clue about what’s going on and a reason why this appeared with Fedora ?
Thank you in advance for your feedbacks.