[Dovecot] Outlook (2010) -> Dovecot (IMAP) >10x slower with high network load and many folders

[Stuart Henderson]

On 2012-04-06, Thomas von Eyben <thomasvoneyben at gmail.com> wrote:
> I am seeing a >10x as slow performance when trying to complete a
> "send/receive" from an Outlook 2010 client to Dovecot via IMAP, but
> only when the LAN is fully loaded with other traffic, EG file copying.
> It seems the problem is when outlook is trying to identify folders
> that have changed since last "send/receive" thus traversing the
> hierachy.

Not sure why it would only affect Outlook clients, but if your
switches are managed, you might like to check if flow control is
enabled and, if so, try disabling it.