Running Civi 5.10.4 and Drupal 7.65.
One of our staff reported that they received an error message when they tried to send out a mailing to attendees at one of our events, through CiviEvent > Email all participants.
She sent out the email at the same time that our monthly newsletter was going out (2500 contacts), and we have a limit set on how many emails are sent per hour. (Settings are below.)
I checked Drupal error logs and found this log but I have no clue what it means:
Deprecated function CRM_Event_BAO_Event::checkPermission, use CRM_Event_BAO_Event::getAllPermissions. Array ( [civi.tag] => deprecated )
I'm thinking our staff member got an error message because she sent out the email at the same time that we had our newsletter queued for delivery, but haven't been able to find any confirmation of this (or any information on why her CiviEvent email to 12 people wasn't just queued to be delivered after the newsletter was delivered).
Would appreciate help on interpreting that error message, or modifying settings so that this doesn't happen again. I guess a workaround solution is to ask staff not to send emails out at certain times to allow the newsletter to go out, though ideally I'd be able to do this without affecting other staff member's workflows.
EDIT: The adjacent error messages are as below (with a variety of referrers, all 'page not found' errors):