We're trying to migrate from our in house Exchange server to Office 365 and when trying to change the SMTP settings for Web Help Desk we notice a 10-20 second delay when trying to submit request tickets, before the confirmation page appears.
I have tried the suggestion from this article 18 second delay in sending outgoing mail (Exchange) to set the Scheduled E-Mail Delivery Threshold to 0, but this has not resolved our issue.
Thinking it may have been a DNS issue I also tried one of Microsoft's IP addresses for smtp.office365.com (discovered using traceroute). The relay works but it still has a delay.
Also, I tried relaying through a free Gmail account, but the delay seems to be related to any external SMTP server.
Anyone have some suggestions for troubleshooting the issue?