Error at checkout

[sbonaime]

Just after I click on "Check-out equipment" button I have the following error

We're sorry, but something went wrong. We've been notified about this issue and we'll take a look at it shortly.

here is the log.

I, [2019-06-19T11:48:10.003295 #4856]  INFO -- : Started PUT "/reservations/checkout/1" for 10.2.5.78 at 2019-06-19 11:48:10 +0200
I, [2019-06-19T11:48:10.005171 #4856]  INFO -- : Processing by ReservationsController#checkout as HTML
I, [2019-06-19T11:48:10.005331 #4856]  INFO -- :   Parameters: {"utf8"=>"✓", "authenticity_token"=>"JwPh2KEeaW9WF0zDItV3bszGny9f9Qww8Tk9NEeJX7tjZQodL8aqbIwQOFcpKteDYqkVA2OmllLZzGwL7CRjog==", "reservations"=>{"5"=>{"equipment_item_id"=>"5", "notes"=>""}}, "commit"=>"Check-Out Equipment", "user_id"=>"1"}
I, [2019-06-19T11:48:10.068412 #4856]  INFO -- :   Rendering user_mailer/reservation_status_update.html.erb
I, [2019-06-19T11:48:10.069777 #4856]  INFO -- :   Rendered user_mailer/_checked_out.html.erb (0.5ms)
I, [2019-06-19T11:48:10.070567 #4856]  INFO -- :   Rendered user_mailer/reservation_status_update.html.erb (2.0ms)
I, [2019-06-19T11:48:10.075187 #4856]  INFO -- : Sent mail to XXXX@YYYY.ZZ (3.8ms)
I, [2019-06-19T11:48:10.075435 #4856]  INFO -- : Completed 500 Internal Server Error in 70ms (ActiveRecord: 28.8ms)
F, [2019-06-19T11:48:10.076417 #4856] FATAL -- :
F, [2019-06-19T11:48:10.076477 #4856] FATAL -- : Errno::ECONNREFUSED (Connection refused - connect(2) for nil port 25):
F, [2019-06-19T11:48:10.076520 #4856] FATAL -- :
F, [2019-06-19T11:48:10.076557 #4856] FATAL -- : app/controllers/reservations_controller.rb:325:in `block in checkout'
app/controllers/reservations_controller.rb:324:in `each'
app/controllers/reservations_controller.rb:324:in `checkout'

I checked and Reservation server does not try to connect to the smtp server. It could be the same error as #1773

[sbonaime]

same problem and solution as #1773