Back up to the Email Features Category


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Jump to: navigation, search is our backup email server. It will accept email for a domain we handle email for and will queue messages and will attempt to deliver to the higher priority MX record.

Spam Protection does do spam checking and will defer email that looks like it is spam in some way. It will deny (cause a permanent delivery failure) messages/connections under the following circumstances:

  • Invalid HELO
  • Recipient domain is not one we handle email for
  • Message size is over 1GB.
  • The server will 'greylist' hosts. It will always defer (cause a temporary delivery failure) messages/connections under the following circumstances:
  • Sending host in a DNS blocklist
  • Header syntax errors
  • Recipient rejected by the primary MX (It does a call back to the primary MX if it is available)
  • Senders email address can't be verified
  • Contains malware (including spam/phish signatures) as picked up by the virus scanner
  • If the SpamAssassin spam score is over 6

The reason for deferring is so the sender is forced to use a higher MX, where it can then make the decision whether to accept or deny the message. -This gives customers running their own servers more control over spam.


Messages will be attempted to be sent on to a higher priority (i.e. lower MX record) email server starting at every 15 minutes, and increasing over time to every 3 hours. It will carry on trying for 31 days before bouncing the message back to the sender.


To force tertiatry-mx to attempt to relay stored messages, telnet in on port 25 and issue an etrn command in the form of


For example:

$ telnet 25
Trying 2001:8b0:0:30::51bb:1e1d...
Connected to
Escape character is '^]'. ESMTP Thu, 08 Sep 2016 09:30:29 +0100
220-Mail accepted subject to terms on 
220 You are 2001:8b0:0::1
250 OK
221 closing connection


If you would like to use as a backup mail server for your domain please contact sales who will add the domain.

If you manage your own DNS server, once added at our end, then you'll want to add an entry similar to:   MX   50