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Posts Tagged ‘port’

Having Problems Sending Email Because Your ISP is Blacklisted?

Wednesday, October 9th, 2013

It happens over and over — users trying to send legitimate email messages are blocked from sending because the IP address that they are getting from their Internet Service Provider (ISP) for their personal computer (or small office) is on some major blacklist, like SpamHaus.  Comcast, for example, has been the focus of many of these issues. This message blocking often happens even if a user is sending outbound email through a legitimate email provider like LuxSci.

Users invariably ask:

  • Why is the mail blocked even though I am sending through LuxSci or some other email provider and not directly from my ISP?
  • What can I do about it?

Fortunately, there is a good reason why the blocks occur and an easy solution to them … anonymous SMTP service to hide your IP address.

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Tags: alternate port, anonymous, blacklist, block, blocked, comcast, ip address, isp, port, port 25, private smtp, received, sending email, smtp, spam, spamhaus
Posted in Business Solutions, LuxSci Library: The Technical Side of Email
5 Comments »

Alternate SMTP Ports – Send Email From Any Location

Tuesday, September 10th, 2013

When sending outbound email from an email program (like Outlook or Thunderbird) or from a mobile device (like iPhone or Blackberry) that is not using Premium MobileSync, your program or device connects to our outbound email servers using an Internet protocol called “SMTP” (The Simple Mail Transport Protocol).

An email server, however, does lots of different things in addition to sending outbound email.  It may allow checking of email via POP or IMAP, or checking your address book using LDAP, or other things. So, when your email program connects to the server it has to specify what it wants to do (i.e. send an email).  It does this by connecting to a numbered “port” on the server.  Port number “25” is the Internet standard for “regular outbound email”.

However, because port 25 is standard for outbound email, many ISPs, wifi networks, hotels, airports, and other locations that provide Internet access will arbitrarily block any connections to servers (except perhaps their own) on port 25 in order to stop spammers from using their services for the sending of spam, viruses, or malware and to prevent their IP addresses from being black listed.

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Tags: 25, 465, 587, alternate port, anonymization, block, firewall, ip addreess, port, smtp, smtp port, ssl, tls
Posted in LuxSci Library: Email Programs and Devices, LuxSci Library: The Technical Side of Email
3 Comments »