Incoming and outgoing SMTP

This page details the configuration for Incoming SMTP

The outgoing (remote delivery) is implemented in the RemoteDelivery mailets. The configuration details for outgoing SMTP traffic can be read on this page (section RemoteDelivery) and shoud be update in the mailetcontainer.

SMTP Configuration

Consult smtpserver.xml in GIT to get some examples and hints.

The SMTP service is controlled by a configuration block in the smptserver.xml. The smtpserver tag defines the boundaries of the configuration block. It encloses all the relevant configuration for the SMTP server. The behavior of the SMTP service is controlled by the attributes and children of this tag.

This tag has an optional boolean attribute - enabled - that defines whether the service is active or not. The value defaults to "true" if not present.

The standard children of the smtpserver tag are:

A list of address:port separed by comma - This is an optional value. If present, this value is a string describing the IP address to which this service should be bound. If the tag or value is absent then the service will bind to all network interfaces for the machine on port 25. Port 25 is the well-known/IANA registered port for SMTP. Port 465 is the well-known/IANA registered port for SMTP over TLS.
Set to true to support STARTTLS or SSL for the Socket. To create a new keystore execute: keytool -genkey -alias james -keyalg RSA -storetype PKCS12 -keystore /path/to/james/conf/keystore.
Please note that each SMTP/LMTP server exposed on different port can specify its own keystore, independently from any other TLS based protocols.
This is a required tag with an optional body that defines the server name used in the initial service greeting. The tag may have an optional attribute - autodetect. If the autodetect attribute is present and true, the service will use the local hostname returned by the Java libraries. If autodetect is absent or false, the body of the tag will be used. In this case, if no body is present, the value "localhost" will be used.
This is an optional tag with a non-negative integer body. Connection timeout in secconds.
Set the maximum simultaneous incoming connections for this service.
Set the maximum simultaneous incoming connections per IP for this service.
Enables proxy support for this service for incoming connections. HAProxy's protocol ( is used and might be compatible with other proxies (e.g. traefik). If enabled, it is *required* to initiate the connection using HAProxy's proxy protocol.
(deprecated) use auth.announce instead. This is an optional tag with a boolean body. If true, then the server will announce authentication. If this tag is absent, or the value is false then the client will not be prompted for authentication. Only simple user/password authentication is supported at this time. supported values: true: announced only to not authorizedAddresses false: don't announce AUTH. If absent, *authorizedAddresses* are set to a wilcard to accept all remote hosts. announce: like true, but always announce AUTH capability to clients Please note that emails are only relayed if, and only if, the user did authenticate, or is in an authorized network, regardless of this option.
This is an optional tag. Possible values are:
* never: Don't announce auth.
* always: always announce AUTH capability to clients.
* forUnauthorizedAddresses: announced only to not authorizedAddresses
Please note that emails are only relayed if, and only if, the user did authenticate, or is in an authorized network, regardless of this option.
This is an optional tag, defaults to true. If true, authentication is not advertised via capabilities on unencrypted channels.
This is an optional tag, defaults to true. If false, AUTH PLAIN and AUTH LOGIN will not be exposed. This setting can be used to enforce strong authentication mechanisms.
Provide OIDC url address for information to user. Only configure this when you want to authenticate SMTP server using a OIDC provider.
Provide url to get OIDC's JSON Web Key Set to validate user token. Only configure this when you want to authenticate SMTP server using a OIDC provider.
Claim string uses to identify user. E.g: "email_address". Only configure this when you want to authenticate SMTP server using a OIDC provider.
An OAuth scope that is valid to access the service (RF: RFC7628). Only configure this when you want to authenticate SMTP server using a OIDC provider.
Optional. An OAuth introspection token URL will be called to validate the token (RF: RFC7662). Only configure this when you want to validate the revocation token by the OIDC provider. Note that James always verifies the signature of the token even whether this configuration is provided or not.
Optional. Provide Authorization in header request when introspecting token. Eg: `Basic xyz`
Authorize specific addresses/networks. If you use SMTP AUTH, addresses that match those specified here will be permitted to relay without SMTP AUTH. If you do not use SMTP AUTH, and you specify addreses here, then only addresses that match those specified will be permitted to relay. Addresses may be specified as a an IP address or domain name, with an optional netmask, e.g., 127.*,,, and localhost/8 are all the same See also the RemoteAddrNotInNetwork matcher in the transport processor. You would generally use one OR the other approach.
This is an optional tag with a boolean body. This option can only be used if SMTP authentication is required. If the parameter is set to true then the sender address for the submitted message will be verified against the authenticated subject. Verify sender addresses, ensuring that the sender address matches the user who has authenticated. It will verify that the sender address matches the address of the user or one of its alias (from user or domain aliases). This prevents a user of your mail server from acting as someone else If unspecified, default value is true.
This is an optional tag with a non-negative integer body. It specifies the maximum size, in kbytes, of any message that will be transmitted by this SMTP server. It is a service-wide, as opposed to a per user, limit. If the value is zero then there is no limit. If the tag isn't specified, the service will default to an unlimited message size. Must be a positive integer, optionally with a unit: B, K, M, G.
This sets whether to enforce the use of HELO/EHLO salutation before a MAIL command is accepted. If unspecified, the value defaults to true.
WARNING: This is Non-RFC compliant (default value: true) See:
This sets the SMTPGreeting which will be used when connect to the smtpserver If none is specified a default is generated
The configuration handler chain
Set the maximum count of boss threads. Boss threads are responsible for accepting incoming SMTP connections and initializing associated resources. Optional integer, by default, boss threads are not used and this responsibility is being dealt with by IO threads
Set the maximum count of IO threads. IO threads are responsible for receiving incoming SMTP messages and framing them (split line by line). IO threads also take care of compression and SSL encryption. Their tasks are short-lived and non-blocking. Optional integer, defaults to 2 times the count of CPUs.
Set the maximum count of worker threads. Worker threads takes care of potentially blocking tasks like executing SMTP commands. Optional integer, defaults to 16.

OIDC set up

James SMTP support XOAUTH2 authentication mechanism which allow authenticating against a OIDC providers. Please configure auth.oidc part to use this.

We do supply an example of such a setup. It uses the Keycloack OIDC provider, but usage of similar technologies is definitely doable.

Configure Authenticated SMTP (SMTP AUTH)

Authenticated SMTP is a method of securing your SMTP server. With SMTP AUTH enabled senders who wish to relay mail through the SMTP server (that is, send mail that is eventually to be delivered to another SMTP server) must authenticate themselves to Apache James Server before sending their message. Mail that is to be delivered locally does not require authentication. This method ensures that spammers cannot use your SMTP server to send unauthorized mail, while still enabling users who may not have fixed IP addresses to send their messages.

Mail servers that allow spammers to send unauthorized email are known as open relays. So SMTP AUTH is a mechanism for ensuring that your server is not an open relay .

At this time Apache James Server only supports simple user name / password authentication.

Configuring Apache James Server for Authentication SMTP is a multi-step process. It requires several adjustments of the smtpserver.xml. To enable SMTP AUTH, do the following:

  1. As mentioned above, SMTP AUTH requires that Apache James Server be able to distinguish between mail intended for local delivery and mail intended for remote delivery. Apache James Server makes this determination by matching the domain to which the mail was sent against the <DomainList> component, configured by Domain List Configuration.
  2. set the authRequired element of the smtpserver configuration block to "true".
  3. if you wish to ensure that authenticated users can only send email from their own account, you may optionally set the verifyIdentity element of the smtpserver configuration block to "true".
  4. Restart Apache James Server. This will pull in all of your configuration changes.

Finally, you need to verify that your configuration was done correctly. This step is important and should not be skipped.

Verify that you have not inadvertently configured your server as an open relay. This is most easily accomplished by using the service provided at will check your mail server and inform you if it is an open relay.

It is extremely important that your server not be configured as an open relay. Aside from potential costs associated with usage by spammers, connections from servers that are determined to be open relays are routinely rejected by SMTP servers. This can severely impede the ability of your mail server to send mail.

Of course it is also necessary to confirm that users and log in and send mail through your server. This can be accomplished using any standard mail client (i.e. Thunderbird, Outlook, Eudora, Evolution).

Configure multiple SMTP servers

LMTP Configuration

Consult lmtpserver.xml in GIT to get some examples and hints.

The configuration is the same of for SMTP.

By default, it is deactivated. You can activate it with SMTP and bind for example on port 24.

The default LMTP server stores directly emails in user mailboxes, without further treatment.

However we do ship an alternative handler chain allowing to execute the mailet container, thus achieving a behaviour similar to the default SMTP protocol. Here is how to achieve this:

  <lmtpserver enabled="true">
    <handlerchain coreHandlersPackage="org.apache.james.lmtpserver.MailetContainerCmdHandlerLoader">
      <handler class="org.apache.james.lmtpserver.MailetContainerCmdHandlerLoader"/>

Note that by default the mailet container is executed with all recipients at once and do not allow per recipient error reporting. An option splitExecution allow to execute the mailet container for each recipient separately and mitigate this limitation at the cost of performance.

  <lmtpserver enabled="true">
    <handlerchain coreHandlersPackage="org.apache.james.lmtpserver.MailetContainerCmdHandlerLoader">
      <handler class="org.apache.james.lmtpserver.MailetContainerCmdHandlerLoader">
      <handler class="org.apache.james.lmtpserver.MailetContainerHandler">