Dispatcher reported workload in the Atlantic Sector that was approaching unworkable; citing system automation issues as contributory.

Narrative

Although I have been working the Atlantic region for over 13 years; it was my 4th day of system training on a live sector. The amount of workload on these sectors contributed to the event that follows. The flight encountered a reroute in the oceanic region and I provided the crew the updated route but mistakenly included both AX20N and ZX20N on the new eastbound flight plan. The pace and tempo required to keep up with the workload is such that these mistakes can be easily made. It was a typical night on the Atlantic sectors with a number of reroutes; turbulence requiring crew updates; and weather amendments. No irregularities and it was all I could do to manage situational awareness at its minimum. Operational control was a real challenge and I was not very effective in providing the crews the support they need to ensure the safety of flight. The main contributors to the lack of situational awareness is the numerous work arounds and labor intensive requirements of the system as well as the information overload from the messaging tool. Over 1;400 messages were produced in an 8 hour shift via the messager. These are messages I have to go through and disseminate and the majority doesn't pertain to the flights in this Atlantic region.