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Mail ports allowed by different ISP’s

Ports 25, 26 blocking

E-mail ports 25 are the ports which are mainly used to send e-mails. It is unsecured and thus it is blocked by many of the ISP’s (Internet Service Providers), so that the amount of spam which is sent from their networks should be cut down. It allows you to block the mails and due to this your mail cannot be send to the other party. It is like, when you try to send mails and if they are blocked by E-mail ports 25, then you may get an error or message in your outbox. This happens because all the mails send between e-mail client and e-mail server via web or internet and is routed through E-mail ports 25,which serves as a medium or channel between them. Now a day’s E-mail ports 25 blocking becomes an industry standard. Instead of the remote SMTP server or a SMTP server running on your computer, SMTP server is needed by the ISP’s to block E-mail ports 25. Look at the few ISP’s who block E-mail ports 25 they are BellSouth MSN, Comcast, NetZero, Charter, Cable One, People PC etc. With E-mail ports 25, there is another E-mail ports 26 also available and If you want to change E-mail ports 25 to E-mail ports 26, then you are required to change your e-mail software and outgoing SMTP E-mail ports settings.

Port 587 allowed by Comcast

Port 587 is a port which is recommended by industries and it is supported by Comcast. Port 587 is mainly used for sending mails to others. The protocols which are used with the port are ESMTP (SMTP-MTA, ESMTP) but there are few additions and restrictions are also there. Even it is suggested to use port-587 instead of port-25 for e-mail client and server’s configuration.

Ports allowed in mail servers

If we talk about E-mail servers, then there are two kinds of mail servers, one is Incoming mail server used for receiving e-mails from others in your inbox and related with your e-mail address account and it cannot be more than one. Now another one named as Outgoing mail server which is mainly used for sending mails to others through your outbox.

After understanding about mail servers, now next question arises in our mind “What are E-mail ports”. In terms of networking, E-mail ports may be defined as an endpoint to a logical connection. The E-mail ports which are allowed in the mail servers are different for both the mail servers i.e. for incoming mail server and for outgoing mail server. Mainly in the case of incoming servers, POP3, HTTP (Hyper Text Transfer Protocol), IMAP E-mail ports are allowed and for outgoing mail servers, SMTP (Simple mail transfer protocol) E-mail ports is used for sending mails. Now every E-mail ports have a no., which is mainly used for its identification and to know its type. Here come few default e-mails E-mail ports, which are allowed in mail servers with their E-mail ports no. SMTP – E-mail ports 25, HTTP – E-mail ports 80, Secure IMAP (IMAP4-SSL) – E-mail ports 585, IMAP4 over SSL (IMAPS) – E-mail ports 993, POP3 – E-mail ports 110, IMAP – E-mail ports 143, Secure SMTP (SSMTP) – E-mail ports 465, Secure IMAP (IMAP4-SSL) – E-mail ports 585, Secure POP3 (SSL-POP) – E-mail ports 995.

Difference between Port- 465 & Port- 587

Port-465 and Port-587 both are used for sending e-mails and this is the similarity between them. But there are some differences also between them.

Port 465 is mainly used for sending e-mails, i.e. it is allowed in outgoing mail servers and it is for SMTP (Simple mail transfer protocol). Before any level of SMTP communication is started, SSL encryption is automatically started. Without any verification, Standard SMTP port accepts e-mails from other mail servers.

Port 587 is used for msa, which is very much like standard SMTP port. If your server provides support, STARTTLS command at SMTP level may start SSL encryption. MSA restricted the outgoing of e-mails in the form of spam when net masters of DUL ranges can block outgoing connections to SMTP port. MSA also accept e-mails after verification e.g. after SMTP authentication.


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