NOTE: This post refers to email subscriptions on forums hosted by Nabble. There are other potential issues where Nabble is providing an archive for a mail list hosted elsewhere. e.g. Post Not accepted by Mailing List
There is a potential problem for those who use want to use Nabble as a conventional mail list server. In such cases people will subscribe to a forum and post their messages by email.
The trouble is that Nabble assumes you are using an email service, such as Gmail, where messages are displayed in "conversations" so you see both copies of the emails you send and their replies in similar fashion to "Threaded View" on the forum.
In consequence Nabble does not, by default, return email posting as part of the subscription as it assumes that your "sent" copy will display to you as part of the conversation.
This is an annoyance for those using conventional mail programs that separate inbound and sent mail and who rely on all mail from a mail list being readable in their Inbox.
If you get complaints from your users about missing mail and want Nabble to behave like YahooGroups, Mailman and most other mail list software, then you can modify Nable's behaviour by editing the "should_get_instant_mail" macro to look like this: