Днес, един от клиентите ни е в Лондон и не можеше да изпрати писмо през smtp (Outlook Express). За целта ми се обади и разгледах случая. Оказа се, че при доставчика му пишеше:

To protect you and our network, we restrict access to port 25 on our Mobile Broadband network.

If you use email software such as Outlook or Vista Mail and your email provider uses Port 25 for outgoing mail, you will need to change your port or SMTP server when connected to our broadband network.

Errors you might see when trying to send email over Port 25 on our network include: SMTP 554 Transact Failed -- Transaction failed; Port 25 error; The connection to the server has failed- Error Number: 0x800CCC0E; or the sending of email will time out.

If you have one of these error messages the best option is to change the outgoing email port from 25 to 587. It is possible that your email provider does not support port 587 -- in which case you should try port 465 as an alternative.

Changing the port number on Outlook Express

Наложи се да добавя още един порт в случая 587 за outgoing smtp

Ето как става най- лесно:

Файл /etc/postfix/master.cf
587      inet  n       --       --       --       --       smtpd