v15+ TPS scheduled reports - ambiguous 'Error sending email' message

Hi everyone,

Since our v15 upgrade a handful of scheduled reports have been consistently failing to send, and the only error they display in the View Reports screen is 'Error sending email for request Id 'XXXXXX' The report itself runs fine and can be viewed within the application, but the email functionality is failing.

Does anyone have any insight or breadcrumbs as to what causes this problem, or what this error actually means? I've seen reports fail to send but then fix themselves a few days later, or in other cases building an identical copy of the schedule to an identical recipient list works fine for some reason. I'd love to get any sort of lead on how to resolve, or pinpoint whether there's any local email environment issues at play (we're on RAMP).

Thanks!