Slow local network performance for image attachments

Jeff Larsen jlar310 at
Sat Mar 29 00:19:53 EDT 2008

On Fri, Mar 28, 2008 at 10:19 PM, Alain Spineux <aspineux at> wrote:
> On Sat, Mar 29, 2008 at 2:09 AM, Jeff Larsen <jlar310 at> wrote:
>  > I run cyrus imap in a virtual machine at home using fetchmail to pull
>  >  my ISP mail into a local imap store. For the most part it works great.
>  >  But with messages that have digital photo attachments it takes a
>  >  seemingly inappropriate long time for Thunderbird to download the
>  >  message (over local wired 100Mb network) and display the pictures.
>  >
>  >  I've got plenty of memory overhead on both the virtual machine and the
>  >  VMware Server host. While in the process of downloading an image
>  >  email, the CPU usage goes higher than I would expect (20%) for a
>  >  simple file transfer. It takes 10-15 seconds to load a message with 3
>  >  images totaling  5MB over non-encrypted port 143. It's 2 or 3 times
>  >  that long if I use imaps on 993.
>  >
>  >  The VMware host is a 2GHz Pentium, with very little load from other processes.
>  First I thing about a probleme with Vmware or hardware (disk access or network)
>  Find the file that match your email in your imap spool, and try to
>  download/upload it using
>  scp on your workstation, and measure the time.

4 seconds via sftp (with encryption) vs. 24 seconds (I measured more
precisely) via Thunderbird imap without encryption.

>  Also try using imap client on your server, and other imap client ....

Squirrelmail on localhost:. very fast, in the blink of an eye,
likewise with Outlook Express (perish the thought).

So I guess it's Thunderbird. That sucks. I guess I'll take this to a
Thunderbird forum. Thanks for pointing me in the right direction. Some
days after troubleshooting everyone else's computer problems, there's
nothing left in the tank for my own...


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