Mac's cant send email anymore

Question

Hello All, hope this is the correct forum to post this issue.
Windows / Mac network
I’ve been sending email with Mac’s and PC’s without a problem for years.
Email is received via pop3 and sent via SMTP port 25.
The network firewall is set to allow any LAN to WAN traffic to pass though.
This setup has worked fine for at least 2 years.
Within the last 2 weeks the Macs have stopped sending emails, still receiving mail but not sending mail.
Sending and receiving email from the PC’s works fine without any problems.
When I check the firewall logs they say the SMTP traffic is passing through.
When I disable the firewall, sending email from the mac work fine.
You would think the firewall would be at fault, although no settings have changed on the firewall to cause a problem. Emails sent from the macs up intill 2 weeks ago had no problem with the firewall.
Is it possible the mac’s would have downloaded a software /OS update to cause this problem?
We have tried setting up the email on a brand new mac straight from the box, the sending problem still occurred .
Has anyone heard of a problem like this?

Answer 1

Sending a mail using their web interface is different than using a client (like your Mac's Mail, or Entourage, etc.)
There are settings in Mail's preferences that have to match your ISP's criteria, exactly.
Look at your MailPreferences, and see if you find the settings that match these steps. This is from the FAQ at WowWay:
Here is critical information you will need to set up your e-mail account:
Type of Incoming e-mail server = POP3
Location of Incoming pop3 server = pop3.mail.wowway.com
Location of outgoing SMTP server = smtp.mail.wowway.com
Your account username = the first letter of your first name, followed by your entire last name, followed by the LAST four digits of your account number (e.g. jdoe9251)
Your account password = the last six digits of your account number (e.g. 229251) Note: your account number can be found on your monthly invoice or on your installation work order.
To setup your email in Outlook Express; please follow the instructions below
1. Open Outlook Express then, click Tools, then Accounts
2. Select the Mail tab and click Add, then click Mail. The Mail wizard displays
3. Enter your Display name and click Next to continue in the wizard.
4. Enter your Email Address and click Next.
5. Enter the following settings, and then click Next:
6. Incoming Mail POP3: pop3.mail.wowway.com
7. Outgoing Mail SMTP: smtp.mail.wowway.com
8. Select the Remember Password option and enter your Account Name and Password. Then, click Next.
9. Click Finish
Mac Mini   Mac OS X (10.4.8)   1x Win2000, 6x WinXP, 3x Linux