100k tickets per day is only 1.4/s (but, you would assume more during day etc), however, interactive Agents working on those tickets would also need to be many to handle the volume. Therefore you'll likely want a few servers for them load-balanced to ensure adequate speed. Depending on the complexity of the tickets and how long each takes to finish etc.If you went Amazon, you would definitely want the S3 plugin, and an auto-scaler for the EC2 instances, and a huge RDS instance in your VPC to accommodate such a volume of tickets..You would have to figure out the SES config yourself, or ensure your email infrastructure can handle that volume.. (There is a pull that might help: https://github.com/osTicket/osTicket/pull/3932) Notifications alone would put most people on the blacklist!