I get “You don’t have permission to access /imp/compose.php on this server” error when trying to send e-mail in horde webmail
Had some interesting error that caused by mod security.
When trying to send e-mail following error appears:
Forbidden You don't have permission to access /imp/compose.php on this server
Forbidden You don't have permission to access /imp/basic.php on this server. Apache Server at webmail.mydomain.com Port 80
There can be also similar error in apache error log file:
[error] [client 22.214.171.124] ModSecurity: Access denied with code 403 (phase 2). Match of "eq 0" against "MULTIPART_UNMATCHED_BOUNDARY" required. [file "/etc/httpd/conf.d/mod_security.conf"] [line "70"] [msg "Multipart parser detected a possible unmatched boundary."] [hostname "HOSTNAME"] [uri "/horde/imp/compose.php"] [unique_id "8m0u-n8AAAEAAD7blhoAAAAO"]
Very likely you have something like mod_security installed which is improperly flagging the request. There is basically no way this can be something IMP is doing.
Configure mod_security properly or disable it from apache configuration.