Office365中提供了将一个Exchange Online Distribution List转化为Office365 Group的方法。
在升级之前，可以先用Get-EligibleDistributionGroup命令来检测哪些Group可以被升级。之后在Exchange Online管理页面，到recipients -> Groups下面，在Upgrade Distribution Lists下点击Get Started.
在弹出页面选择一个或者多个想要升级的Group. 之后点击Start to Upgrade就可以开始升级了。如果选择的Group不符合可以被升级的需求，会有对话框弹出提示。
升级过程可能会需要几分钟到几小时。我测试使用了一个只有两个Member的Group,只花了几分钟。有意思的是中途刷新页面看到升级过程中，新创建的Group在原来Distribution List名字后面加了个1，不过之后升级结束之后这个1就去掉了。Convert生成的新Group带有一个Alias, 其中一个Alias是原来的Distribution List名后加了个1.
升级之前我设置的是允许外部用户向这个Distribution List发送邮件，升级之后的Office 365 Group仍然保留了这个设置。并且之前向这个Distribution List发送的邮件也被转移到了新生成的Office365 Group Mail Box中。试验了分别向带1和不带1的Group Name发送邮件，都可以成功收到。
关于不能升级为Office365 Group的Distribution List, 可以在以下列表中找到。
| Property |
Eligible? |
| On-premises managed distribution list. |
No |
| Nested distribution lists. Distribution list either has child groups or is a member of another group. |
No |
| Distribution lists with member RecipientTypeDetails other than UserMailbox, SharedMailbox, TeamMailbox, MailUser |
No |
| Distribution list which has more than 100 owners |
No |
| Distribution list which only has members but no owner |
No |
| Distribution list which has alias containing special characters |
No |
| If the distribution list is configured to be a forwarding address for Shared Mailbox |
No |
| If the DL is part of Sender Restriction in another DL. |
No |
| Security groups |
No |
| Dynamic Distribution lists |
No |
| Distribution lists which were converted to RoomLists |
No |
除了在升级页面进行操作，也可以使用PowerShell进行批量升级。Office 365 Group具有Email Distribution Group所具有的功能，同时提供和SharePoint, Calendar, One Note等的集成，所以对于之前创建的有协作需求的Distribution List，确实提供了一个很好的升级转化途径。可见的是，有的Distribution List确实只有邮件分发的作用，对这种Distribution List可选择不升级。