Roller Network Help - Mail Services
Roller Network offers a highly configurable and flexible mail handling service. This series of documents explains our methodology, features, and how to use them.
Minimum Requirements to Receive Messages
All control is handled through the account control center. A domain may be operated filter-free by disabling all available options. However, there are some minimum requirements that all incoming mail is subject to. These establish a known baseline of minimum conditions.
If you need to change settings to your mail domain, choose "Change Service" from the actions selector. Never delete and re-add your mail domain to change settings or to try and "fix" a delivery issue; all settings will be lost. Contact us for help if you believe you have a delivery issue.
There are several service modes for a mail domain:
Secondary MX
A Secondary MX mail domain acts as a backup according to its given MX priority. If the lowest priority server is unreachable, messages will be sent to the higher priority servers where they will wait until the lowest priority server is available. Use equal priority MX records for our servers.
Secondary MX Settings:
SMTP Redirection (Direct Delivery)
SMTP Redirection (Direct Delivery) allows you to send messages to servers on ports other than 25 or have our filtering and mail handling tools act as a front-end filter to your mail server. The destination server can be entered as a DNS host name or as an IP address; using IP address mode allows you to bypass stale DNS records.
Important: Although you can enter a DNS host name as the delivery destination, direct IP address delivery is much more reliable. Transports with unresolvable DNS are dropped by Postfix. Use our IP Address Helper feature to automatically update your SMTP Redirection domain as an IP destination when using a host name, or use Mail Mirror to store backup copies. Roller Network is not responsible for lost mail due to host name destinations.
This mode is interchangeable with Secondary MX; the difference is SMTP Redirection (Direct Delivery) will ignore MX records and deliver to the configured server or IP address. This is useful if your mail domain is normally in Secondary MX mode, but you've changed the IP address of your server and want mail delivery to resume without waiting for DNS to update.
SMTP Redirection (Direct Delivery) Settings:
SMTP Redirection (Lookup Record)
Like direct delivery SMTP Redirection, the Lookup Record variant also can also deliver to alternate ports. However, unlike Direct Delivery, the Lookup Record mode will use DNS records to determine where we should connect for message delivery. You can use this mode for multiple destination servers on your end using round-robin DNS (multiple A records or equal priority MX records) and primary/secondary delivery (MX records).
SMTP Redirection (Lookup Record) Settings:
The "Lookup Record" is a DNS record that will be used by our servers for your delivery rules. Here's some examples in BIND format where "lookuprules.example.com" is the Lookup Record you would configure in our system.
Please note: because lookup records are always specific to the situation they are required for there is no "standard" setting that Roller Network support staff can advise to use. Some generic examples are given below.
Round-robin DNS to IP addresses:
lookuprules.example.com IN A 1.2.3.4 lookuprules.example.com IN A 5.6.7.8 |
Distributed delivery using MX records:
lookuprules.example.com IN MX 0 server1.example.com lookuprules.example.com IN MX 0 server2.example.com lookuprules.example.com IN MX 0 dynamic.example.com |
Primary/Secondary delivery:
lookuprules.example.com IN MX 0 server1.example.com lookuprules.example.com IN MX 0 server2.example.com lookuprules.example.com IN MX 5 server3.example.com lookuprules.example.com IN MX 5 server4.example.com |
Hosted Mail Domain
A hosted mail domain is one that uses our hosted mail boxes for delivery. As the name implies, we're hosting email for you. Unlike the above modes, you do not need your own mail server for a hosted mail domain.
Hosted Mail Domain Settings:
You will need to configure hosted mail boxes when using this mode.
Forward All Messages to Email Address
Mail can be forwarded to another address by using "Forward All Messages to Email Address" mode. Any message arriving for a mail domain in this mode is resent to the configured email address. Forwarded messages are counted for resource usage.
Forward All Messages to Email Address Settings:
Existing messages in the mail queue can't be forwarded to an external email address on a mail domain mode change.
Forward All Messages to Mail Box
This mode will forward all messages for a mail domain in this mode to one of our hosted mail boxes. Mail box forwards are not counted for resource usage.
Forward All Messages to Mail Box Settings:
Existing messages in the mail queue can't be forwarded to a mail box on a mail domain mode change.
Accept and Hold Messages
Accept and Hold Messages mode allows our system to accept messages as normal and hold them in the queue. This is normally used if you're performing maintenance on your mail server or to place an emergency stop on incoming mail for any reason. When switching out of this mode, you can only deliver to the following modes: Secondary MX, SMTP Redirection (Direct Delivery), SMTP Redirection (Lookup Record), or Hosted Mail Domain. (Forwarding is not possible because it takes place pre-queue.)
Accept and Hold Messages Settings:
Accept and Hold Messages will keep queued messages for three weeks.
Regardless of the mode chosen, all mail services include a large selection of filtering, handling, and forwarding options. Backup queuing is included with every mode whenever the final destination cannot be reached.
In some cases it is desirable to artificially limit the number of connections we will try to make or throttle large delivery bursts into smaller groups. When a domain has "Slow Delivery" enabled, the system will limit the number of simultaneous connections and increase timeouts. This option is helpful when the final destination is on a slow connection, bandwidth limited, or for slow mail servers. When combined with SMTP Redirection, this option can be used to limit the flow of incoming messages to a manageable rate. The flow of messages will be buffered and released in a controlled, sequential manner.
Slow delivery should also be used if there are an abundance of "connection timed out" messages in the outgoing mail logs. The default connection timeout is 2 seconds; slow delivery increases the connection timeout to 45 seconds. Since this option will artificially delay mail delivery, sometimes up to several hours, it should not be used unless required. (This option may be set by Roller Network operations staff if a destination is having trouble receiving queued messages due to congestion or network timeouts.)
In order to utilize the Roller Network mail services, the DNS records for the domain name must include proper MX records. Depending on the service used (Secondary MX, SMTP Redirection, etc.), different MX priorities are utilized. Some accounts are eligible for advanced or dedicated servers; a full list of available SMTP servers is shown on the Resource Access page.
Equal priority MX records for the Roller Network mail servers should be used. Not only does this distribute load across our incoming paths, it also prevents false rejection scanner errors. (We have internal hardware load balancers to handle redundancy internally.) Equal priority MX records still roll over to others of the same priority if one is unavailable.
Example - Roller Network as a Secondary MX:
example.com IN MX 0 yourserver.example.com example.com IN MX 5 mail.rollernet.us example.com IN MX 5 mail2.rollernet.us |
Example - Roller Network as your mail host (SMTP Redirection, Hosted Mail Domain):
example.com IN MX 0 mail.rollernet.us example.com IN MX 0 mail2.rollernet.us |
We can only support configurations where both "mail" and "mail2" are present in the MX records for a domain. Using a single MX record is unsupported and may have undesirable results if the listed server is unavailable.
Test messages can be submitted directly to our mail servers by using the Mail Domain Tests tool.
Advanced options for a domain can be configured by choosing "Advanced Options" from the action selector. Check the "Apply" box by each advanced option you wish to apply to selected domains. To disable a previously configured advanced option, set it to its default value.
Maximum Message (DATA) Size
Our servers can allow up to 100MB (104857600 bytes) messages. If your server doesn't support large messages, configure the maximum allowed size in bytes here. If an incoming message is too large, it will be rejected with the message "DATA size of [received size] bytes exceeds maximum of [configured size] bytes". The default is "0 bytes" for no limit.
RCPT TO Response Delay
This option will create an artificial delay after the first RCPT TO command in the SMTP session. A value of "0" (zero) seconds disables this option. The maximum allowed delay is 90 seconds.
The Recipient Delimiter (also know as Address Extensions) option allows address extensions to be changed from the default delimiter of "+". If you use address extensions, this setting should be changed to match the delimiter that you use. The default of "+" is the most common, but - (single dash), . (single dot), and + or - are also available. If you don't use address extensions, leave this setting to the default "+".
This option is not supported for mail box delivery in Hosted Mail Domain mode. Hosted mail boxes only recognize the "+" delimiter for address extensions.
The Include Subdomains option allows a mail domain include subdomains. By default, mail domains do not include subdomains of the domain name configured in the account control center. When enabled, a subdomain will be rewritten to its parent domain and processed normally. Example: for mail domain "example.com" with subdomains enabled, mail coming in on "sub.example.com" would be rewritten to "example.com". The most specific match will win, so you can still add subdomains to your account with a different configuration than the parent domain with Include Subdomains.
Domains with Include Subdomains enabled will appear before other domains in the mail domain lists.
Trim Message (DATA) Size To
The Trim Message (DATA) Size To option will trim (truncate) a message delivered to SMTP paths (i.e. Secondary MX, SMTP Redirection, Hosted Mail Domain) while leaving the original size intact for forwarding and mirroring. Both headers and body can be affected if a trim byte limit is applied as the entire message is treated as a whole. This option is useful to only pass a fixed maximum size to the final destination without rejecting. As it is not multipart aware, attachments and multiparts may be silently broken. When a message is subjected to the trim option it will be logged in the mail logs and the notice ** Trimmed to ### bytes ** will be appended to the end of the body (although it may only be visible in the message source if a large attachment was cut off). The DATA portion passed may be slightly larger than the trim value due to normal header expansion; rejecting based on the trim value is not supported.