What is the requirements of mail server

You need to remove that link from your sig.

Keep It Spam-Free
Do not spam, advertise, plug your website, or engage in any other type of self promotion. To encourage open, unbiased (incentive-free) discussion, it is prohibited to refer to sites you own or are affiliated with outside of the Business Exchange category. Additionally, keeping discussions anonymous encourages more open conversation, because members are not afraid of revealing their strategies to their competition.

All forums contained within the Business Exchange category are sorted based on thread start time and cannot be bumped. To ensure these sections remain non-spammy, please try to limit yourself to one new thread per month within each of these forums.

Only the direct sale of unique (ie one-of-a-kind) items or services is permitted within the aforementioned forums. Only items within the seller's immediate possession may be sold or traded. Please do not link to off-site eCommerce sites or auctions. No affiliate links are permitted anywhere within DaniWeb (except within forum signatures). Self-promotion links are permitted within forum signatures provided they do not contradict with any other sitewide rules, such as inappropriate language or content.

What will happen: The offending unsolicited post will be deleted (or plugged URLs snipped).
First offense - plug: Member will be warned via user infraction system. Warning will be documented.
Second offense - plug: 5 point infraction will remain on user's record for 3 months.
First offense - solicitation: 5 point infraction will remain on user's record for 3 months.

first yum install sendmail*
then chkconfig sendmail on
then service sendmail restart
then go to the file called vim /etc/mail/sendmail.mc type dnl in 116 line and uncommand #
then m4 /et/cmail/sendmail.mc > /etc/mail/sendmail.cf just convert to machine language.
then give vim /etc/mail/local-host-names
here give stationx.example.com
mail.example.com wq ie., save&exit
give chkconfig sendmail on
and service sendmail restart
after this givve command or go to the file vim /etc/mail/access
here give for example ( RELAY) wq ie., save&exit
and type chkconfig sendmail on and service sendmail restart
at last type vim /etc/aliases here just type for example john: john,jane
wq ie., save&exit and mail to john
and type newaliases before chkconfig sendmail on and service sendmail restart.
This is the things u want in sendmail services.