Net::SMTPServerBusy happened in: Hackathons::DigestMailer#digest

### [Incident: #150](https://appsignal.com/hack-club/sites/64dc848fd2a5e4d7b35c5ca2/exceptions/incidents/150/traces/last) Net::SMTPServerBusy happened in: Hackathons::DigestMailer#digest

**Message**

```
454 Throttling failure: Maximum sending rate exceeded.

```

**Backtrace (up to last 10 lines)**

```
lib/net/smtp.rb:1036 Net::SMTP#check_response
lib/net/smtp.rb:981 Net::SMTP#data
lib/net/smtp.rb:799 block in Net::SMTP#send_message
lib/net/smtp.rb:926 Net::SMTP#rcptto_list
lib/net/smtp.rb:799 Net::SMTP#send_message
lib/mail/network/delivery_methods/smtp_connection.rb:53 Mail::SMTPConnection#deliver!
lib/mail/network/delivery_methods/smtp.rb:109 block in Mail::SMTP#deliver!
lib/net/smtp.rb:643 Net::SMTP#start
lib/mail/network/delivery_methods/smtp.rb:154 Mail::SMTP#start_smtp_session
lib/mail/network/delivery_methods/smtp.rb:108 Mail::SMTP#deliver!
```

View on AppSignal: https://appsignal.com/hack-club/sites/64dc848fd2a5e4d7b35c5ca2/exceptions/incidents/150/traces/last

Start at Hackathons::DigestMailer#digest and trace the SMTP delivery path through lib/mail/network/delivery_methods/smtp.rb, smtp_connection.rb, and lib/net/smtp.rb. Review the AppSignal incident and reproduce or inspect the sending-rate failure; done when digest delivery no longer fails with Net::SMTPServerBusy under the relevant conditions.

Written by the indexing model from the issue text.