You can configure static catalog access instead of creating catalogs dynamically.

ID: InstanceStaticLoginsType

Static authentication

Specifies that authentication is statically configured

ID: InstanceStaticLoginsType.Auth (references: LoginType)

Impersonated

The service account is also used to authenticate to the statically configured mailboxes. Otherwise, the entries in the static catalog must have a fully configured authentication.

ID: InstanceStaticLoginsType.Impersonated

Static mode

This value determines whether the statically configured mailboxes should be processed with impersonation or separately or whether they should be used as forwarded journal recipients.

ID: InstanceStaticLoginsType.StaticMode (references: StaticCatalogType)