Often you run into quota issues on standalone dovecot installations. Here’s how you check quota for each individual mailbox and reset it if needed:

doveadm quota get -u user@domain>

Change quota by editing the database table corresponding to the quota settings. This can be found out by checking the dovecot.conf configuration file and the database query corresponding to the ‘quota’ plugin.

Restart dovecot and recalculate the quota by using the following command,

doveadm quota recalc -u user@domain>

Check quota again to confirm,

doveadm quota get -u user@domain>

Quota name Type Value Limit %
user STORAGE 262 10485760 0
user MESSAGE 55 10000 0

You should be good to go.