archive my emails

Typically you do not have to archive your emails, because there is a backup system. Saving disk space (on the mail account) is also 'normally' not necessary.
If you leave the institute and you loose your IMATH and also the UZH email address, it might me necessary to make a copy of your mails.
Attention: copying emails is slow! Please be patient, check the log messages what's going on.
There is no 'one solution fits all'.
Copy to a mail folder of a different email account (gmail, gmx , ..) - Via Thunderbird, Apple Mail, ...
Quick and easy solution.
Drawback:
Not so stable if you have thousands of emails.
If you have subfolders: there is no recursive duplicating - you have to do it for every single folder.
Step by step:
Setup any email client on your computer. F.e. 'Thunderbird' (http://www.mozilla.org/en-US/thunderbird/) or Apple Mail. Configure your IMATH Account.
Copy (duplicate!) all mails (mark all mails and choose 'copy') to
a) a local email folder (this becomes your archive/backup, which is stored on your local computer), or
b) a second configured (a free email service like gmail, gmx, ...) email account.
In most applications, you have to copy/duplicate each folder separately (no recursive copy).
Thunderbird: use importexporttools-ng
Create a zip or mbox file(s) of your mails - thunderbird#Import_.2F_Export_Mails:_importexporttools-ng
Via imapsync
https://github.com/imapsync/imapsync
Commandline tool - no GUI - compplicate to setup
Has to be installed locally.
Very flexible.
Copies Mail recursively.