On 03/31/2017 12:03 AM, Shawn Heisey wrote: > Dovecot package version is 1:1.2.15-7+deb6u1. It is in Debian 6.0.10, > using the Debian package. > > The server is in my basement at home, and is exposed to the Internet so > I can fully access my mail from anywhere. I use IMAP for reading mail. > > I have a number of folders in my mailbox that have thousands of messages > in them, from mailing lists. > > When I'm at home, I have a LAN connection to the server. It goes > through a Cisco firewall that limits the connection speed to 100Mb/s. > In this situation, I can open a folder with 25000 messages in it, click > on the next unread message that Thunderbird did not know about before, > and within a second or two, the message will download, allowing me to > view it and reply. > > When I'm at work, with highly variable network latency between > Thunderbird and the server, doing exactly the same thing takes a LOT > longer. I have seen it take as long as 15 minutes for a single message. > If I open a folder with only a few messages in it, it is fast. > > The server is not overloaded -- I can log into it with ssh and use "mutt > -f" to open a folder directly. Loading thousands of messages into mutt > takes a while, but I have no difficulty using the ssh connection and > running commandline programs. > > This suggests that the IMAP communication between the server and the > client involves a large amount of back and forth communication when the > message count in the folder is high, possibly something for every > message in the folder. It happens quickly on a LAN but crawls on a > connection with high latency. I can understand it taking a few seconds > longer on a high-latency link, but it takes minutes. > > I do plan on building a new server and migrating to Dovecot 2.x, but I > haven't had the time to work on that. > > Is this a known problem? If so, is it fixed in 2.x? > > Thanks, > Shawn This sounds like your companies firewall trying a mitm attack or similar. Just a wild guess.
If the SSH-connection is good (probably ignored by the firewall or maybe even prioritized), then forward your IMAP-traffic through it and see if the problem persists. This is not meant as a solution, but to help analyze the problem. # ssh -L 10993:127.0.0.1:993 [email protected] Then connect with Thunderbird to 127.0.0.1:10993. You could also use :143, the SSH-tunnel is already encrypted. Greetings Daniel
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