Various limits for message size which will be accepted by Kerio MailServer can be set. All in all, the server includes three limit types.
The first is a limit for SMTP server that applies to all messages delivered via SMTP. This rule applies to messages forwarded from other SMTP servers as well as to messages from SMTP clients (this implies that the limit applies also to too large messages sent from Kerio MailServer where sending through SMTP protocol is set).
Another type is a limit for sent messages. This limit can be either set for a particular user (such a user who overloads the line by sending too large messages) or for an entire domain. This limit type does not apply only to messages delivered to the server via SMTP protocol, but also to all outgoing messages (i.e. it applies also to WebDAV interface, etc.).
The third limit type applies to messages sent from the Kerio WebMail interface. The purpose of this limit is focused in section 18.1.4 Size limit for Kerio WebMail.
To set size limit for email received by the SMTP server, go to the administration interface:
Open the
section.Go to the Security options tab.
Check and set the Max. number of failed commands in SMTP session: option.
To set a limit for a particular user, use the Kerio MailServer's administration console:
In
, open the dialog for change of user parameters.Switch to the Email tab.
Check the Limit outgoing message size to option and set a size limit.
If the limit is set to 0
, Kerio
MailServer behaves the same way as if no limit was set.
To set a limit for a particular domain, use the Kerio MailServer's administration console:
In
, open the domain selection dialog.Switch to the Email tab.
Check the Limit outgoing message size to option and set a maximal size limit (in MB).
If the limit is set to 0
, Kerio
MailServer behaves the same way as if no limit was set.
Setting of maximum message size can be used for the following purposes:
to limit size of attachments sent to Kerio
WebMail by an HTTP POST
request,
to set maximum size of memory allocated in Kerio
MailServer to each HTTP POST
request.
Maximal value of the limit is 128 MB. It is not possible to enter a greater value in the Kerio Administration Console.
For better understanding of the limit, here is an explanation of how
a message written in Kerio WebMail is sent to
Kerio MailServer. Each new message composed in the web
interface is sent by a browser via HTTP protocol using an HTTP
POST
request to Kerio WebMail. The interface
receives the message and processes it so that Kerio
MailServer can send it to the addressee by SMTP protocol.
Each HTTP POST
request contains one message
including a message body, all headers and attachments. The limit set by
this option narrows size of any HTTP POST
request directed
from the Kerio WebMail interface to Kerio
MailServer. This means that any limit set for requests also limits
size of email messages.
Size limit set for HTTP POST
requests is applied
to any files sent from Kerio WebMail to Kerio
MailServer and it is applied to all Kerio
MailServer users. The default value for maximum size of messages
sent from Kerio WebMail is 20 MB. This limit should be
generally satisfactory for these purposes.
The minimum value for the limit is 2 MB. If a lower limit is set, Kerio MailServer sets the value back to 2 MB automatically.
If a message includes any attachments, they are encrypted by the
Base64
method. This type of encoding is able to increase the
size of transmitted data even by one third (in case of binary data). This means
that, for example, the minimum 2 MB limit might also allow just 1 — 1,5
MB attachments.
It is necessary that a memory allocation value is specified in
Kerio MailServer for HTTP POST
requests. The more bulky the request is the more memory must be allocated. This
implies that the size of the allocated memory changes according to changes in
the size limit.
Any time the limit is changed, it is necessary to restart Kerio MailServer since the memory allocation is changed as well.
To set limit for email sent via Kerio WebMail, open the Kerio MailServer's administration interface:
Open the Configuration → Advanced Options section.
Switch to the WebMail tab.
Check the Maximum size of message that can be sent from the WebMail interface option and set a value for the limit.