Is it possible to disable the MageMail extension entirely?
However, I know how it is when you're trying to troubleshoot a strange problem and you want to rule out everything possible, even though you know they *shouldn't* be causing the problem.
So, MageMail degrades pretty gracefully when disabled. You can disable the module entirely (app/etc/modules/KJ_MageMail.xml) in order to rule it out as a cause of the problem.
When the module is disabled:
- New emails will not go out
- Links will not be broken in emails that went out previously
- Coupons that were sent in emails can still be used.
Things that won't work:
- Coupons will not be auto-applied when a customer clicks through. But they can still manually apply them.
- Auto-login won't work
- The promotion bar won't show up when they click through - Images may be broken in past emails that went out (if Settings > Advanced > Product Image Controller is enabled which is usually should be)