We recommend using standard FTP software over a browser for transfering your files.

For Windows we recommend FileZilla:
http://filezilla-project.org/download.php

For MacOSX we recommend Transmit:
http://www.panic.com/transmit/

Other examples of such programs (sometimes called utilities) are WS_ftp, Cute_ftp, Fetch, Transmit, etc. Most FTP programs can be downloaded for free or for a small shareware fee from tucows.com

As an alternative, you can use your cPanel File Management utility to upload your web files

File Manager Flash tutorial here

FTP stands for File Transfer Protocol.

Usually the reference is for a program that is designed (only) for transferring files to and from a web server and a hosting account.

For Windows we recommend FileZilla:
http://filezilla-project.org/download.php

For MacOSX we recommend Transmit:
http://www.panic.com/transmit/

Other examples of such programs (sometimes called utilities) are WS_ftp, Cute_ftp, Fetch, Transmit, etc. Most FTP programs can be downloaded for free or for a small shareware fee from tucows.com

This could be due to any number of things. Here are some of the more common
issues why this would occur intermittently:

POP before SMTP. -----------
You are not checking your email account (to receive new messages) before trying to send. There is an option within the newer Outlook versions, "Log on using." (same as the POP3 settings) within Servers ---> Settings ---> Outgoing Mail Server, that will also work for successfully authenticating with the server for sending (without having to check first.) Other email programs may have similar features.

If you ARE using POP before SMTP, i.e. if you are relying on checking before sending authentication, then you will need to keep in mind that the time allowed to send is 30 minutes, afterward you must check again before sending more email.

Server space allocation is full or nearly full. -----------
Either the total disk space allocation is full, or the space for the individual email account user is full or nearly full. Check the cPanel stats for this (side-bar and within the Email Account Management area). If this is true then there may not be enough room on the server to spool up out-bound email messages.

Local hard drive error. -----------
There may be a bad hard drive block (directory error) or full disk situation with your local computer system. This may cause a corruption of the outbound email spool file (on your own computer) and thus the problem.

Bad connection to the internet. -----------
Too much line noise or other interference that is garbling the vital two-way communication (for SMTP authentication) between the your computer and the server. The typical solution is to switch off the computer and then re-seat all the cables.

ISP assigned a bad IP. -----------
Your internet access account could be on a dynamically assigned IP address. And your ISP may occasionally assign a misconfigured IP address, e.g. one with no proper rDNS assigned. This problem used to be rare but is becoming more common as ISPs expand their service. On more than one occasion, we found a LinkSky customer with a misconfigured IP address.

Solution - Order a fixed IP address from your ISP.

Option - Go to http://www.whatsmyip.org and report to us (at help@linkskysupport.com ) the IP that comes up on the first page. Include a description of this issue with your domain name in the subject line. We will be happy to do the research for you. It takes just a few minutes.

ISP port block. -----------
As you probably know, sending email requires a bit more authentication than receiving due to all the spam abuse over the years. This has lead to many ISPs blocking any port 25 transmissions from going through their system without first authenticating with THEIR email server. i.e. in many instances these days there is an additional layer of auth before outbound email transmissions can pass through the ISPs network.

The simple solution for this is to just put your ISPs SMTP server address in the Outlook setup for the sending email host server config. Everything else can be left the same including the domain based reply to email address.

As an alternative you can try setting the SMTP / sending email port within Outlook to use port 426 rather than port 25. This is the alternative port we established just for these occasions, but this does not always work as sometimes the ISP blocks a range of ports.

The intermittent nature of this could be explained this way - Your ISP has begun to convert their entire system for tighter anti-relay (anti-spam) controls, but they have thousands of customers and hundreds of servers which take time. They have this customer on a dynamic (revolving) IP which means that sometimes his email is being routed through a server that blocks port 25 and sometimes it does not.

For more general info about this, try a Google.com search using something like "ISP port 25 block" as a search term.

Outlook parameter file failure. -----------
Intermittent errors like this can be an indication of an Outlook specific error.

Outlook works with a series of behind-the-scenes parameter files that often go corrupt. When this occurs the user can not send email or receive email or both. Sometimes this can be fixed by deleting the account user (from within Outlook) then rebooting the computer and then re-starting Outlook and resetting the user. But actually it is best just to go with a better email client such as Eudora, especially if this is for any kind of business email use. Free copy here http://www.eudora.com

Outlook originated virus infection. -----------
Another giant benefit with NOT using Outlook (any version) is that one is then stepping out of the email virus crossfire as 99% of all email attachment viruses are designed to take advantage of Outlook and all the auto-start, etc. features that Microsoft has incorporated (indeed, these days an Outlook user does not even need to click on an attachment in order to become infected.) Just using Eudora is like installing a super-anti-virus software package, but of course anti-virus software (such as the Mcafee.com anti-virus program) is also recommended.

The reason why we mention this possibility (of a virus infection) in conjunction with this issue is because there are viruses that will attempt to attach copies (of itself/the virus) to any outbound email. This will of course often cause problems with sending email.

This could be due to any number of things. Here are some of the more common issues why this would occur intermittently:

POP before SMTP. -----------
You are not checking your email account (to receive new messages) before trying to send. There is an option within the newer Outlook versions, "Log on using." (same as the POP3 settings) within Servers ---> Settings ---> Outgoing Mail Server, that will also work for successfully authenticating with the server for sending (without having to check first.) Other email programs may have similar features.

If you ARE using POP before SMTP, i.e. if you are relying on checking before sending authentication, then you will need to keep in mind that the time allowed to send is 30 minutes, afterward you must check again before sending more email.

Server space allocation is full or nearly full. -----------
Either the total disk space allocation is full, or the space for the individual email account user is full or nearly full. Check the cPanel stats for this (side-bar and within the Email Account Management area). If this is true then there may not be enough room on the server to spool up out-bound email messages.

Local hard drive error. -----------
There may be a bad hard drive block (directory error) or full disk situation with your local computer system. This may cause a corruption of the outbound email spool file (on your own computer) and thus the problem.

Bad connection to the internet. -----------
Too much line noise or other interference that is garbling the vital two-way communication (for SMTP authentication) between the your computer and the server. The typical solution is to switch off the computer and then re-seat all the cables.

ISP assigned a bad IP. -----------
Your internet access account could be on a dynamically assigned IP address. And your ISP may occasionally assign a misconfigured IP address, e.g. one with no proper rDNS assigned. This problem used to be rare but is becoming more common as ISPs expand their service. On more than one occasion, we found a LinkSky customer with a misconfigured IP address.

Solution - Order a fixed IP address from your ISP.

Option - Go to http://www.whatsmyip.org and report to us (at help@linkskysupport.com ) the IP that comes up on the first page. Include a description of this issue with your domain name in the subject line. We will be happy to do the research for you. It takes just a few minutes.

ISP port block. -----------
As you probably know, sending email requires a bit more authentication than receiving due to all the spam abuse over the years. This has lead to many ISPs blocking any port 25 transmissions from going through their system without first authenticating with THEIR email server. i.e. in many instances these days there is an additional layer of authentication before outbound email transmissions can pass through the ISPs network.

The simple solution for this is to just put your ISPs SMTP server address in the Outlook setup for the sending email host server config. Everything else can be left the same including the domain based Reply-To email address.

As an alternative you can try setting the SMTP / sending email port within Outlook to use port 426 rather than port 25. This is the alternative port we established just for these occasions, but this does not always work as sometimes the ISP blocks a range of ports.

The intermittent nature of this could be explained this way - Your ISP has begun to convert their entire system for tighter anti-relay (anti-spam) controls, but they have thousands of customers and hundreds of servers which take time. They have this customer on a dynamic (revolving) IP which means that sometimes his email is being routed through a server that blocks port 25 and sometimes it does not.

For more general info about this, try a Google.com search using something like
"ISP port 25 block" as a search term.

Outlook parameter file failure. -----------
Intermittent errors like this can be an indication of an Outlook specific error.

Outlook works with a series of behind-the-scenes parameter files that often go corrupt. When this occurs the user can not send email or receive email or both. Sometimes this can be fixed by deleting the account user (from within Outlook) then rebooting the computer and then re-starting Outlook and resetting the user. But actually it is best just to go with a better email client such as Thunderbird, especially if this is for any kind of business email use. Free copy here http://www.mozillamessaging.com/en-US/thunderbird/

Outlook originated virus infection. -----------
Another giant benefit with NOT using Outlook (any version) is that one is then stepping out of the email virus crossfire as 99% of all email attachment viruses are designed to take advantage of Outlook and all the auto-start, etc. features that Microsoft has incorporated (indeed, these days an Outlook user does not even need to click on an attachment in order to become infected.) Just using different email software is like installing a super-anti-virus software package, but of course anti-virus software (such as the Mcafee.com anti-virus program) is also recommended.

The reason why we mention this possibility (of a virus infection) in conjunction with this issue is because there are viruses that will attempt to attach copies (of itself/the virus) to any outbound email. This will of course often cause problems with sending email.

It is most likely that your ISP is blocking transmissions through their system on port 25, the SMTP port. In other words, email transmissions that are not first authorized by your ISPs own internal email system are being blocked. Many of the larger ISP's are now doing this as a spam and email server hijacking prevention measure.

If this is the case, the easy solution for you is to put your ISP's SMTP server address in the sending/outgoing email setting of your email software. You can still use your LinkSky email address as the Reply-To, and essentially keep everything else the same. With this configuration, you will be sending email via your ISP's server, and receiving email via your LinkSky account.

Another thing you might try is to set up your email software to use the alternative port for sending email which we have reserved for port 426.

Also, in any case you are still able to send and receive email via your account's WebMail utility. (Although impractical to use on a daily basis.)

For further reading about ISP port blocks for sending email, try a search at google.com using something like "ISP port 25 block", or "access provider blocking 25".