Webmail is opening very slow, it takes ~40 second to load the webmail page.
From internal network the ping retrieves the following respond:
# ping example.com -f -l 1589
ICMP requests with size more than MTU failed
Bandwidth limiter for Apache
# httpd -M | grep mod_bw
MTU size is not properly set for network.
mod_bwmodule using Plesk autoinstaller and check the access to webmail:
If access to webmail is still loading very slow in internal network, but from external is loading fine, most probably this can means that packets with size more than MTU are not fragmented. Contact system administrator to check the configuration of network equipment since this issue is considered to be Administative Task which is Out of Odin Technical Support Scope .
Please use the link for your reference: