Tickets not sending notifications

Is there an issue with the mechanism that sends out emails? All of a sudden we have stopped receiving any emails from helpdesk. Does this part of the app depend on some external infrastructiure. The log shows email was sent, but I never received an email:

6‎/‎28‎/‎2018‎ ‎11‎:‎51‎:‎12‎ ‎AM started on ticket #1042

Resolved condition values: {}

Condition result: true

Actions runs:
Action #1 “Send email” succeeded
Outcome: Sent email to piotr.prussak@xyz,matthewp@xyz

Hello @Piotr_Prussak, thank you for your message.

We are sorry for any inconveniences, yesterday in the evening there was a problem with our servers, but it should be working now.

We have these emails in our error queue and will resend them in 1-2 hours.