JMAP Settings


The section convers the configuration of JMAP including resource limits as well as E-mail and Mailbox settings.

Request Limits

The following parameters control different limits to be enforced on JMAP requests:

  • max-size-upload: Maximum file size in bytes that can be uploaded. Defaults to 50000000 (~50 MB).
  • max-size-request: Maximum JMAP request size in bytes. Defaults to 10000000 (~10 MB).
  • max-calls-in-request: Maximum number of method calls in a JMAP request. Defaults to 16.
  • max-objects-in-get: Maximum number of objects that can be fetched in a single JMAP Get call. Defaults to 500.
  • max-objects-in-set: Maximum number of objects that can be created, updated or destroyed in a single JMAP Set call. Defaults to 500.
  • query-max-results: Maximum number of results to return in a JMAP Query response. Defaults to 5000.
  • changes-max-results: Maximum number of results to return in a JMAP Changes response. Defaults to 5000.


max-size-upload: 50000000 # bytes
max-size-request: 10000000 # bytes
max-calls-in-request: 16
max-objects-in-get: 500
max-objects-in-set: 500
query-max-results: 5000
changes-max-results: 5000

E-mail Settings

Stalwart JMAP includes a full-text search engine that automatically detects the language of each email when the Content-Language MIME header is absent. In cases where automatically detecting the language of a message is not possible (for example, en email containing just an ambiguous very short sentence), you can set a default language with the default-language setting. This parameter accepts a valid ISO 639-1 language code and its default value is en (English). Example:

default-language: en

Additionally, the following limits can be enforced on JMAP Email objects:

  • mail-max-size: Maximum allowed size in bytes of an e-mail message. Default to 104857600 bytes (100 MB).
  • mail-attachments-max-size: Maximum allowed size in bytes of an e-mail attachment. Default to 50000000 bytes (~50 MB).
  • mail-import-max-items: Maximum number of messages that can be imported on a single Email/import JMAP request. Default to 5 items.
  • mail-parse-max-items: Maximum numbers of messages that can be parsed by a single Email/parse JMAP request. Default to items.


mail-max-size: 104857600 # bytes
mail-attachments-max-size: 50000000 # bytes
mail-import-max-items: 5
mail-parse-max-items: 5

Mailbox Settings

The following limits can be set for JMAP mailboxes:

  • mailbox-name-max-len: Maximum length of a mailbox name. Defaults to 255 characters.
  • mailbox-max-total: Maximum number of mailboxes that a user can create. Defaults to 1000.
  • mailbox-max-depth: Maximum nesting levels for mailboxes. Defaults to 10 levels.


mailbox-name-max-len: 255
mailbox-max-total: 1000
mailbox-max-depth: 10