Different helpdesk logs can be cleaned from here depending upon the date that is selected for the logs.

Settings >> System Section >> System clean up

Clean logs before:

Date and time can be selected and the logs that are present before that particular date selected will be cleaned.

Error log:

All error log file will be cleared.

Sent email log:

It will clear all the sent mail logs for the date that is mentioned for it.

Gateway transactions log:

It will clear all Gateway transactions log for the date that is mentioned for it.

Activity log:

It will clear all Activity log for the date that is mentioned for it.

Audit log:

It will clear all Audit log for the date that is mentioned for it.