We have many customers with massive mailboxes, in the double GB range, which is really bad in many ways, so let's look at a few and discuss the issues.
Bandwidth and Performance
When you have a large mailbox, your email client will have to periodically parse the entire mailbox to ensure its local copy is in sync, this can take a long time, and use up significant bandwidth
from the virtual servers allowance.
Additionally, any errors during this sync process can cause the local copy to be out-of-sync, requiring the client to download the entire mailbox again.
On mobile data this can be slow and expensive.
Search
Many clients implement a search index, which makes searching faster, but mobile clients and those of lesser standing do not, which means any 'search' requires examining every email, and even if this is done server-side (as is possible with IMAP4) the resources are excessive and count towards compute allowance.
Security
Whilst it should never happen, in real life email compromise does happen, and when it does, whoever has obtained your email password
now has access to GB of email's going back over potentially years. This is of course bad on many levels, but primarily
it allows blackmail, extortion and fraud.
We had a customer come to us after their current email with another provider was
compromised, and their customers were told (from that same email) to pay their invoices to another account. This was a
massive problem, and they never did recover all the money. The fraud was made possible because they had 5GB of invoice history
going back over several years together with passwords (never send passwords via email) for online banking, logins to
their account system, and more.
The more email you have, the more risk you have.
The Solution
Most good email clients have an archive feature, which takes email and moves it to local folders somewhere after a period of days.
This is a great way to archive email, keep it secure locally and reduce bandwidth and compute costs.
If you want something
more automated then GEN offers email archiving as a service, where we take email after a set period and bundle it up into
either a single mailbox with folders for each user, a single archive file with emails as files, or several native file formats
such as inx or pst.
Another option which works well is our auto-clean service whereby the user creates folders to store
email they wish to keep, e.g. by customer or by process, and then auto-clean can be setup to delete anything left in the inbox
that is older than 30 days for example. This is a great way to maintain email housekeeping and to organise your inbox.
Whatever you choose, having a mutli-GB mailbox is not a good idea.