Brian Cryer's Glossary of IT Terms with Links
Backup Mail Server
- Backup Mail Server
- A secondary email server to which emails are delivered should the primary
email server be offline. A backup email server will
then forward emails to the primary email server once the primary email server
comes back on-line.
When an email server is down most sending email servers will retain the email and try sending again later. Generally most servers will give up and issue a non-delivery notification (NDR) to the sender after about two days (the actual time varies between servers). So even without a backup mail server emails will normally be delivered if the mail server is down for a short period of time. A backup mail server provides resilience where:
- The sending server has a very short timeout before giving up and issuing an NDR.
- The server will be down for a long period - as a guide anything over a day or so.
In these scenarios a backup mail server will receive emails and ensure that they are delivered once the primary mail server comes back on-line.
For more information see:
- www.cryer.co.uk/brian/msexchange/exch_as_a_backup_email_server.htm - How to set-up Exchange 2003 as a backup email server for another site.