Linux admin (mainly centos, apache, postfix, mysql 4 and 5, dns, ipv6, Atlasian tools and more..)

I am looking for a skillful admin to help me upgrade and improve my server(s). Mainly centos, apache, postfix, mysql 4 and 5, dns, ipv6 and more.. Working with Atlasian tools (at least JIRA) as user is required knowledge. Knowing administration of Atlasian tools is advantage. This is likely job for 1-3h per day for 1-3month and maybe longer. I have 3 Trial tasks - choose one to solve, the other - explain why NOT choosen for solving. Feel free to ask me for email and for more info during shaping your solution. Situation - shared hosting with hundreds of hosted domains. 1. apache server - from time to time /tmp volume (1G size) is running out of space. How will you solve it? 2. postfix server - one of hosted domains gets flooded with stream of tens to hundreds of emails to non-existing users per minute, the active queue grows to thousands of emails... What is your solution?