Unable to send emails

Please help.  I setup CWP and everything seems to be working.  I installed wordpress and none of the emails are sending out.  I think it may have something to do with how my dns and postfix manager are setup.  I do not understand it very well.  Its running on a VPS. I can see all the emails getting stuck in postfix mail queue.

here are some of the errors I see.

(Host or domain name not found. Name service error for name=server.mydomain.info type=A: Host found but no data record of requested type)

(host mta5.am0.yahoodns.net[63.250.192.45] said: 553 5.7.1 [TSS07] Connections will not be accepted from xxx.xxx.xxx.xxx, because the ip is in Spamhaus's list; see help.yahoo.com (in reply to MAIL FROM command))
                                         useremail@yahoo.com


Thanks to all.

a good mail server have the following set up :
> rdns
> mx record
> DKIM and SPF entries

check if it is configured or not

(host mta5.am0.yahoodns.net[63.250.192.45] said: 553 5.7.1 [TSS07] Connections will not be accepted from xxx.xxx.xxx.xxx, because the ip is in Spamhaus's list; see help.yahoo.com (in reply to MAIL FROM command))
                                         useremail@yahoo.com
Thanks to all.

Your ip blacklisted by Spamhaus, need to unlist if possible, can do by yourself or ask vps provider. Otherwise, find other provider with clean IP.

This is what I have now.

(host mx00.gmx.net[xxx.xxx.xxx.xxx] refused to talk to me: 554-gmx.net (mxgmx009) Nemesis ESMTP Service not available 554-No SMTP service 554 invalid DNS PTR resource record, IP=xxx.xxx.xxx.xxx)
personemail@gmx.com

I dont really understand how to setup

rdns
mx record
DKIM and SPF entries


I am a little new at this and was only used to cpanel.  Can someone help me set them up please ?