What ports should be open

[glennbtn]

Hi

We have installed Zimbra on a public hosted server. We can send and receive most mail. Some companies that we need to send email to use places like mimecast.com. When we send email to these it just sits in the box, if we disable the firewall (apf on centos) the mail goes out.

Can anyone make a suggestion as to why this is when mail that usually goes to a company mail server direct has no issues.

Many thanks

[phoenix]

The only outbound port required to send email is Port 25 the SMTP port.

Ports - Zimbra :: Wiki

[glennbtn]

Thanks for that. Not sure why these server only accept mail when the firewall is off even though 25 etc is open

[phoenix]

It's not recommended that you run a firewall on the Zimbra server although you should protect it with one, perhaps you should investigate your IPTABLES rules and see if it's blocking anything outbound. There's also this in the wiki: Firewall Configuration - Zimbra :: Wiki

[SpiderTech]

Another port for SMTP is 587. I notice some SMTP servers block 25 for spam reasons.

[phoenix]

Originally Posted by SpiderTech

Another port for SMTP is 587. I notice some SMTP servers block 25 for spam reasons.

Port 587 is the Submission port, that is the correct port for mail clients to submit mail for delivery. It's not the SMTP port, that is port 25 and is used by mail server to connect to each other. Port 587 can be used if a mail forwarding service is sending mail to a server because port 25 is blocked by an ISP.