MailHop Relay

This guide will help you set up the MailHop® Relay service.

What is MailHop Relay?

MailHop Relay is an e-mail redelivery service. It accepts mail for your domain, scans the messages for spam and viruses, then transmits the mail to your server over a variety of optional ports (to circumvent blocks on SMTP traffic). The service also features many optional DNSBLs to stop known bad senders, user lists, white- and blacklisting, and includes MailHop Backup MX to prevent lost mail during downtime.

MailHop Relay is not a standalone service; it redelivers mail to a mail server which you own and operate. If you wish to receive mail for your domain, but do not want to host your own mail server, you can use our MailHop Forward service instead.

How do I set it up?

Please complete the following steps to get started with the MailHop Relay service. This guide assumes that you are using our domain registration and Custom DNS services, though they are not required to use MailHop Relay.

1. Create MailHop Relay

The first step is to create the MailHop Relay service for your domain, e.g. mydomain.com. You will be prompted to select a destination mail server (the hostname where your server is located, e.g. mail.mydomain.com); a destination relay port, such as 25 or 2525; and optional message filtering options such as spam scanning, virus elimination and DNSBLs. After purchase, please wait fifteen minutes for the service to activate.

Important! Mail received by MailHop Relay is pre-tagged with the destination mail server and port. If your server is unavailable, we will retry delivery using the original port and destination. If you change the port or destination mail server later, stored mail will continue to be redelivered to the original location.

At this time, we cannot re-tag stored mail; for this reason, we suggest using an alternate port when possible (in case your ISP begins blocking 25) and never use an IP address as the destination mail server (if you use a hostname, you can change the host's IP and mail will be delivered to the new address).

2. Configure your MX records

To allow MailHop Relay to receive email for your domain, you will need to add mx1.mailhop.org and mx2.mailhop.org as the primary and secondary MX records for your domain. If you are using Custom DNS, you may simply click the Set for MailHop button on your DNS configuration page. If you are using third-party DNS or the Expert interface, your MX records should be:

Host TTL Type Data
example.com 43200 MX 10 mx1.mailhop.org
example.com 43200 MX 20 mx2.mailhop.org

You may include additional mail servers in the MX records for your domain, but mx1.mailhop.org must be the primary and mx2.mailhop.org must be secondary or lower. Please note: If mx1.mailhop.org is not the highest priority mail server, it will detect the actual primary server and resend the message without processing it (i.e. no spam scanning or alternate port relaying). If mx2.mailhop.org is used as the primary, it will reject mail to sender.

3. Configure your mail server and network

If you are using an alternate port, you will need to open the new port in your firewall software, such as Windows Firewall or Norton Internet Security. You will also need to add the new port forwarding rule to your router. (For more information, please see PortForward.com for a list of guides by router.)

You will also need to configure your mail server to accept the incoming mail from MailHop Relay. If you are using anti-spam features such as tarpitting and greylisting, or using physical anti-spam devices such as a Barracuda to filter your mail, you will need to whitelist our MailHop Relay servers to avoid accidental rejections. You can view our full range of IPs here.

If possible, enter these addresses under the "trusted forwarder" section of your mail server or anti-spam device; this will allow your server to properly scan mail delivered to your server without blacklisting MailHop Relay.

I need to change settings while mail is queued.

If MailHop Relay receives a message, but is unable to deliver that message to you, the message is tagged with the destination port and hostname, then queued for redelivery.

If you change the destination hostname or port in your Relay service, mail still stored in backup will continue to be delivered on the original hostname and port. For example, if you have your service set to mail.domain.com on port 2525, and you move to a new location and set up your server on 10025, MailHop will still try to deliver stored mail to 2525.

Since messages cannot be re-tagged once received, it is very important to keep the hostname and port the same after downtime. If the original port is disabled for some reason (new network, ISP port blocking, etc.), you will need to set up a temporary server on the original port in an unrestricted network to "flush out" the stored queue. (New messages will be tagged with the updated configuration.)

Please also note that the service tags by port and hostname; you can change the IP for your hostname to a new location without any adverse effects on mail delivery. This is why it is strongly recommended to create MailHop Relay for a hostname, not an IP address, as mail queued for that IP cannot be re-tagged if the IP changes.

Troubleshooting

Mail delivery problems can often be difficult to troubleshoot, as there are many points along the way where a message could be delayed, rejected, or even silently dropped without the sender ever knowing a problem occurred. Please check the following entries to see if they describe your problem; if not, you can contact our support team for further help.

When contacting Support, please send the full headers of any delayed or rejected emails (including timestamps and Received: entries) where available, and describe the timeframe of the problem to the nearest hour with timezone. Please make sure you contact Support using an email address outside of the problem domain to make sure we can contact you!

Mail is delayed for hours, then arrives all at once.

This is a symptom of greylisting, where a mailserver will temporarily reject mail (4xx error) to deter spammers. You must whitelist our MailHop Relay addresses in your server to prevent these delays.

My mail is being rejected with a 550 User Unknown error.

Unless MailHop Relay explicitly receives a 5xx Permanent Failure error from your server, we will not reject email with this form of error. Please review your mail logs to determine if your server is misconfigured before contacting Support, and be sure to provide any strange snippets of logs and full headers from the rejected emails.

There are many potential causes of this problem, but here are some of the most common:

My mail server is down. How often do you try to redeliver my mail?

For the first 24 hours after a failure is detected, we try to redeliver your mail every 15 minutes. For the next four days, we retry delivery every hour. For the remaining five days, we retry every two hours. After ten days, stored mail is bounced back to sender.

I receive a lot of mail. What are the queue size and message size limits?

MailHop Relay does not limit the total volume of individual messages it can store or redeliver. MailHop Relay has a per-message size limit of 10MB; individual messages larger than 10MB will be returned to sender with a useful error message.

I'm getting spam for mailboxes that don't exist.

Your server does not have recipient filtering enabled. Recipient filtering checks to make sure a receiving address exists before accepting the content of a message, returning a 550 User Unknown error to the sender for nonexistent mailboxes. Without recipient filtering, your server will accept any email, then later send a non-delivery report (NDR) back to the origin (a waste of time with spam).

As mentioned above, MailHop Relay uses call-aheads to verify that a mailbox exists before accepting and redelivering the message to you. By enabling recipient filtering, you reduce the load on both your server and ours as we block nondeliverable mail right at the start. Exchange users can learn how to enable recipient filtering here. Customers can also use the User List in MailHop Relay to block invalid recipients at the service level.

I'm getting a lot of spam. Can I block more of it with MailHop Relay?

MailHop Relay includes a variety of anti-spam options. By utilizing these features, you can drastically reduce the amount of spam delivered to your server via MailHop Relay. Simply lowering the Tag Limit and Discard Limit of your service by a few points each can result in a significant drop in spam.

I want to use an anti-spam service like Postini as well as Relay.

Unfortunately, you cannot use MailHop Relay and a third-party anti-spam service simultaneously. You can learn more about this here.