IIRC o servidor de e-mail que o Ubuntu usa por padrão é exim4
e provavelmente já está instalado. Use dpkg-reconfigure exim4-config
de um terminal raiz.
De esta (seção 8.5.3) :
If you would like your system to also handle external e-mail, you will need to reconfigure the exim4 package[22]:
# dpkg-reconfigure exim4-config
After entering that command (as root), you will be asked if you want split the configuration into small files. If you are unsure, select the default option.
Next you will be presented with several common mail scenarios. Choose the one that most closely resembles your needs.
e o texto descreve algumas opções:
internet site
Your system is connected to a network and your mail is sent and received directly using SMTP. On the following screens you will be asked a few basic questions, like your machine's mail name, or a list of domains for which you accept or relay mail.
mail sent by smarthost
In this scenario your outgoing mail is forwarded to another machine, called a “smarthost”, which takes care of sending the message on to its destination. The smarthost also usually stores incoming mail addressed to your computer, so you don't need to be permanently online. That also means you have to download your mail from the smarthost via programs like fetchmail.
In a lot of cases the smarthost will be your ISP's mail server, which makes this option very suitable for dial-up users. It can also be a company mail server, or even another system on your own network.
mail sent by smarthost; no local mail
This option is basically the same as the previous one except that the system will not be set up to handle mail for a local e-mail domain. Mail on the system itself (e.g. for the system administrator) will still be handled. local delivery only
This is the option your system is configured for by default.
Já que você está em um local de trabalho, parece que você não terá um problema enviando e-mails SMTP da porta 25. Assim, você pode selecionar "site da Internet". Observe, no entanto, que você coloca sua empresa em risco de ser colocada em uma lista negra se seus aplicativos PHP forem indevidamente usados para spam, etc. Assim, para uma camada adicional de proteção, talvez você queira configurar uma conta de e-mail em algum lugar e usá-la como um smarthost durante o teste. Exim irá enviar e-mail de saída através deste smarthost.