Workmail redirect issues

Moving some companies mail management using Workmail , but also to other functions in AWS. Though , Workmail is a headache due to poor performance in redirecting incoming emails to external accounts, typically temporary project members. We use one mail account to manage all redirects, creating a group for each external user and adding redirect account to the group. Then in Workmail email rules settings we define all rules. Most are working , especially thoose with one external receiver. But in some distributionlist ( a group) we have some 20 external receivers. The result is that the mail is stored in redirect account mailbox and is stack there. With some 4-5 members in a distribution list the redirection works but creates a lot, some 50, records in "deleted box" where the rules is set to "remove" the mail when sent. Of course there are no problems to redirect mails internally in Workmail. We find it strange that there is no simple and straight-forward redirect function that can be maintained without any IT skills.