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Posts Tagged ‘block’

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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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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Enforcing and Detecting TLS Email Encryption on Inbound Messages

Thursday, June 7th, 2012

SMTP TLS allows email messages to be transmitted from the sender’s email server to the recipient’s over a secure channel that prevents eavesdropping.  TLS is an extremely useful and popular technology as it is seamless —  the sender and recipient do not have to do anything special — and provides a level of server-to-server security important for compliance, HIPAA, and privacy in general.

Use of SMTP TLS requires that both the sender’s and the recipient’s email servers support it.  For example, LuxSci’s servers support TLS and will “talk TLS” to any recipient server that also does.  

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New: Restrict Which Email Addresses Your Users can Receive Email From

Thursday, May 28th, 2009

LuxSci’s new “Sender Restriction” feature allows account and domain administrators to exert firm control over which email is delivered to their users.  When enabled, this feature permits the specification of:

  • An “allowed sender list” of domains and/or email addresses.  Email from anyone not on the list will be refused (bounced back to the sender with an error).
  • An “denied sender list” of domains and/or email addresses.  Email from anyone on this list will be refused (bounced back to the sender with an error).

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