Sitecore ECM 2.1 on Sitecore 7.2 Not Sending Emails when New Relic APM is Enabled

Question

Sitecore Email Campaign Manager 2.1 appears to get stuck on sending emails whenever New Relic APM is Enabled, if New Relic is disabled the Email Campaign Manager sends as usual.

• No errors reported in the Sitecore Logs
• Request just stops processing and that thread never shows up in the log again
• IIS Log shows return codes of 200 so no failures there either
• When performing an IIS reset sometimes the email is received but in a delayed fashion, such as 30 minutes after an IIS Reset

• Below are the logs with Sitecore ECM debug set to true:

  2015-11-18 16:00:57 ManagedPoolThread #4 INFO  Job started: Sending message (56E4501BEE95446BAD97171B3316226F)
  2015-11-18 16:00:57 ManagedPoolThread #4 INFO  EmailCampaign: 'SendAnEmail': 1 recipient is added to the queue.
  2015-11-18 16:00:57 ManagedPoolThread #4 INFO  EmailCampaign: Dispatch Message (SendAnEmail): Started
  2015-11-18 16:00:57 6312 INFO  EmailCampaign:   BodyLink -> GetTargetItemUrl: 00:00:00.0130126
  2015-11-18 16:00:57 6312 INFO  EmailCampaign: Get body link: 00:00:00.0190269
  2015-11-18 16:00:58 6312 INFO  EmailCampaign: Download string content(url): 00:00:00.6889992
  2015-11-18 16:00:59 6312 INFO  EmailCampaign:   ReplaceTokens -> Find/Add $title$ token: 00:00:00.6088072
  2015-11-18 16:00:59 6312 INFO  EmailCampaign: Replace tokens: 00:00:00
  2015-11-18 16:00:59 6312 INFO  EmailCampaign: Remove 'form' tag: 00:00:00.0157781
  2015-11-18 16:00:59 6312 INFO  EmailCampaign: Remove VIEWSTATE: 00:00:00
  2015-11-18 16:00:59 6312 INFO  EmailCampaign: Insert style sheets: 00:00:00
  2015-11-18 16:00:59 6312 INFO  EmailCampaign: Modify 'href' links: 00:00:00.0491805
  

Answer 1

There should be a parameter in the New Relic config:

<browserMonitoring autoInstrument="true" /> 

which is designed to time page download speed to browser.

With this set to true a JavaScript being injected by New Relic monitoring on the SE environment. However, it will do this to ALL web pages generated by .NET including email body.

It is possible that ECM 2.1 cannot correctly process the message body with this script.