Slow local network performance for image attachments

Alain Spineux aspineux at
Fri Mar 28 23:19:00 EDT 2008

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


>  What's gong on here and can I do anything to fix it? Why so much CPU
>  to transfer a 5MB message?. Doesn't Thunderbird handle the mime
>  decoding?
>  We use a similar setup at work (cyrus on virtual machine) for 50 users
>  and I don't have the same problem there. Granted, the hardware is
>  faster, but it's also carrying a much heavier load for other services.
>  --
>  Jeff
>  ----
>  Cyrus Home Page:
>  Cyrus Wiki/FAQ:
>  List Archives/Info:

Alain Spineux
aspineux gmail com
May the sources be with you

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