The problem in a nutshell: Space for mail on the server is limited. If the space is used up, the email account will cease to work (it won't receive new incoming mail) until space is cleared. Here we describe how to clear space by moving old mail off the server into an archive that you store on the main computer you use for business purposes (this should be a device that you keep regularly backed-up). This is known as "archiving your email".
How to archive: The exact process to be followed will depend on the software you are currently using to read and write emails (e.g. Outlook or Thunderbird). The best thing to do is to find out the name and version number of your email software, then go to google.co.uk and search for "archive email in Outlook 2013", for instance, if you are using the 2013 version of Outlook. But, in general, the procedure will involve the following steps:
1. Open the software you use for reading and writing business emails (e.g. Outlook or Thunderbird).
2. Find the settings for your business email account (in Thunderbird click the three-line icon to open the main menu, then click Options to see the menu item named: Account Settings).
3. In the settings, find the section dealing with archives (in Thunderbird, it is included in a section called "Copies and Folders").
4. Look first for the choice of where to create the archives. The archives MUST be created in what are called the Local Folders on your PC. If you don't choose this option, the archives will be created on the server, which completely defeats the object as no space will be cleared.
5. Have a look for further archive options (note the button in the above graphic named: Archive Options). Some email software can be set to automatically archive mail that is over a certain age (e.g. mail that is more than 6 months old). You may or may not want to automate the archive process. Or there may be options for sorting mail into either yearly or monthly folders, as below.
6. Save the new settings if there is a Save or OK button to click.
7. Leave the settings and return to your inbox. If mail has not been automatically archived, start selecting old mail (e.g. all the mail from the previous year). Left-click the first email in the inbox, then hold the shift key while you left-click the last email you want to archive to select those two plus all the mail in between. After selecting the mail, you should be able to see or to find the option to archive the selected mail.
Click that option and wait for the mail to be moved to the archive folder. When the process has finished, you should be able to see the archive folders in the Local Folders section in your email software window, numbered according to the corresponding year. Open one or more of the archive folders to check that the mail you expect to see there is indeed there.
8. Now open the Sent folder for mail, select the old mail that can be archived, and click the option to archive it as well. You should see that moved to a Sent folder for the appropriate year in the Local Folders section of your email software.
9. One last thing: The Deleted folder. If you haven't tweaked your settings to automatically empty this folder, a lot of deleted mail can pointlessly accumulate, so open the Deleted folder, select everything and click the option to finally get rid of it completely.
Tip: Depending on the amount of email you get and send, archive your mail once a year to keep the mailbox well within its limit.
P.S. Remember that if you ever want to check to see what mail is still in the mailbox on the server and how full that is, you have direct access to the mailbox using the webmail facility. Click for a guide to using webmail to check and manage your mailbox on the server.