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Dovecot Limits
Dovecot contains various configurable and built-in resource limits designed to prevent denial of service situations. This page lists those limits.
⚠️ TODO
This list is currently incomplete.
Storage Size Limits
quota_mailbox_count
| Default | 0 |
|---|---|
| Value | unsigned integer |
| See Also | |
| Changes |
|
Maximum number of mailboxes that can be created. Each namespace is tracked separately, so e.g. shared mailboxes aren't counted towards the user's own limit.
0 means unlimited.
quota_mailbox_message_count
| Default | 0 |
|---|---|
| Value | unsigned integer |
| Changes |
|
Maximum number of messages that can be created in a single mailbox.
0 means unlimited.
quota_max_mail_size
| Default | 0 |
|---|---|
| Value | unsigned integer |
| See Also |
The maximum message size that is allowed to be saved (e.g. by LMTP, IMAP APPEND or doveadm save).
0 means unlimited.
See Also
User Concurrency Limits
lmtp_user_concurrency_limit
| Default | [None] |
|---|---|
| Value | unsigned integer |
Limit the number of concurrent deliveries to a single user to this maximum value.
It is useful if one user is receiving numerous mail messages and thereby causing delays to other deliveries.
mail_max_userip_connections
| Default | 10 |
|---|---|
| Value | unsigned integer |
The maximum number of IMAP connections allowed for a user from each IP address.
This setting is checked only by backends, not proxies.
Note that for this to work, any username changes must be done already by passdb lookup (not by userdb lookup).
Unique users are identified via case-sensitive comparison.
Memory Limits
- service configuration (vsz_limit)
- service configuration (process_limit)
- service configuration (client_limit)
Message Headers
There is a 10 MB limit for a single message header block, and a 50 MB limit for all header blocks in a message.
MIME Parts
Maximum number of MIME parts per message is 10000. A maximum of 100 MIME parts can be nested in the same hierarchy path.