I’m seeing some occasional problems with replying to a topic via email, might apply to creating a new topic as well. The problems seem to fall into two categories.
Discourse rejects the email as not coming from a valid email address. This seems to happen on a random basis, which suggests some kind of bug in Discourse. Most of the time it looks like the email address is the primary email address for that user. (I’ve seen one case where AOL substituted aim.com for aol.com in the email address, that appears to be a problem at AOL.) I’m not sure if the user always gets a message letting them know the post didn’t match a valid email address, in testing I did get those messages.
Discourse rejects the email for exceeding the rate limit. This appears to be a Discourse issue caused by how email posting works. Discourse polls the email server every five minutes. If someone sends two posts within a few minutes of each other they might get into the same batch. That appears to cause the second one to reject as a rate limit error because it has only been a second or less since the previous email message was processed. It does not appear that the user gets a reject message, either, so they don’t know it was rejected.
One solution is to use the Discourse interface by logging in at nu-sports.tssi.com using your web browser, that also eliminate the 5 minute delay before the post is processed.