Managing IMAP

UW’s Limitations

All this plug-and-play ability must, of course, come at some price. With UW IMAP, that price is lack of support for some important features and a certain degree of Unix-centricity. Note that we say these are limitations, not necessarily shortcomings. Ultimately the result of the limitations is that UW IMAP is a tightly focused server.

No Support for IMAP Quotas

UW IMAP does not support the RFC 2087 quota extension. That means that, instead of application-specific IMAP quotas, UW IMAP servers must rely on the underlying OS for quotas. The effect is that, with the default Unix MDA, a message delivered to an over-quota UW INBOX is bounced back to the sender. It is not deferred and reattempted later—it bounces hard. On an RFC 2087–compliant server, the message would be held in queue for n days and delivery would be reattempted periodically, until either the usage drops below the quota limit or time runs out and the mail is bounced.^[45]

Many system administrators would prefer that UW IMAP included support for IMAP quotas (RFC 2087) because such support would allow a finer degree of granularity over allocating space in the mailstore to users. A user, for example, could have numerous unrelated quotas that apply to different parts of her personal mailstore. The IMAP quota specification provides for not just one quota, but entire hierarchies of quotas. User joebob might have a quota of 10 MB on his INBOX, a separate overall quota of 30 MB on his entire collection of ...