I have a linode account when i click on DNS manager then edit my domain name there is a section that says Mail Server and written as mail.mydomain.com . Does that mean linode comes with a email server and i dont have to install one?
Also if i do need to install one when installing postfix it asks for a fully qualified domain name, im always unsure what to put for this one. would it be mail.mydomain.com or the default one that comes with linode which is in this format: lixxx-xx.members.linode.com or the domain i want to use like mydomain.com
Linode DNS Manager, as the name implies, only manages your DNS records. There are several types of DNS records, one of which is MX or mail exchanger. You can set up your mail server address and name here. Linode does not (to my understading) set up a functional mail server for you, it your responsibility to configure and maintain one.
When setting up
postfix
, you should put in the same information as is in DNS for your domain. In any case, you can't run a mail server for thelinode.com
domain, and very likely not for any subdomains either, includinglixxx-xx.members.linode.com
.Given your confusion about the matter, I'd suggest you study DNS and SMTP in general, and your mail server in particular. Any active mail server (i.e. anything answering on port 25 or 587) will be tried for possibilities of sending spam, and that will succeed for quite slight misconfigurations.