[dozzie]

Postfix with Dovecot or Cyrus IMAP, along with a good sysadmin.

[ya3ad]

I am don't have much knowledge as system admin. For security measure what action can be taken?

[dozzie]

For 150 users you need a sysadmin. Go and hire one.

[xstartup]

Please stop with this advertisement. Yea, we know you are a sysadmin but whether its 150 users or 1500, it's not you who is going to decide if he needs one or not.

[dozzie]

> Please stop with this advertisement.

And I am advertising what exactly?

> [...] whether its 150 users or 1500, it's not you who is going to decide if he needs one or not.

Indeed, it's not me who decides, it's the reality that decides.