[MU] Mailet to mail to all users

[chibenwa]

Why?

One customer want a mail alias for writing to everybody hosted on the platform (information on the mail service)

Example...

<mailet matcher="RecipientIs=all@govmu.org" class="MailToAllUsers" >
    <batchSize>100</batchSize>
</mailet>

Will replace existing recipients with all users (usersrepositroy.listUsers) as recipient of the email.

This can be contributed into server-mailets

Performance notes

Note that this can cause significant processing as APPENDING emails for one recipient can be a longish operation. Adding a batchSize parameter can be a good idea:

• We treat the first batch of recipients directly says first 100

• Then uses mailetcontext().send(...) to send to all remaining recipients, by groups of 100

  That way we may prevent emails with excessive recipient count and also paralelize the delivery

  Needed when

  ASAP for the code. Deployment with next release is ok.

  Definition of done

  • [x] James ticket
  • [x] PR with unit tests

[quantranhong1999]

https://github.com/apache/james-project/pull/2469

[Arsnael]

Can't just be a group ML with all users part of it? Or they just don't want to bother maintaining such a group list?