What is an email alias
An email alias is another email address which forwards all email which arrives at that address to your main email address. For instance you may be called John but your friends might call you Jonny therefore your email address might be firstname.lastname@example.org but you might want your friends to be able to email you at email@example.com. The second address could be set up as an alias which forwards all email which arrives at it to your main address firstname.lastname@example.org. There is no mailbox associated with an alias, it simply forwards emails onto another address hiding that main address from the sender.
Why might I want one
The above example is a bit contrived. More normally people want aliases so that they don’t have to hand out their main email address to people they don’t trust or suspect they might receive spam from. Thus you may want email@example.com to give out when you are signing up for mailing lists. Or firstname.lastname@example.org for giving to your power company. If you suddenly get lots of spam to an alias the alias can simply be switched off and deleted killing off the spam.
How do I get one
You can simply request any address @mtheory.co.uk from the administrator. Provided it’s not taken already it will be setup to forward to your main email address.