You may experience delays when sending email from your Volusion-hosted email accounts via Outlook or other POP email program resulting in slow email delivery, or even delivery failure. So, what is going on?
Issues with Using POP Clients
If you're using a third-party email solution such as Microsoft Outlook to access your Volusion email, you may be subject to certain restrictions depending on your Internet Service Provider (ISP). Some ISPs require all mail being sent over their system to be routed through their SMTP servers.
One ISP confirmed to do this is AT&T and its affiliates. Any mail sent through a third-party program is forced to be routed through AT&T's SMTP server. If you use Outlook (for example, mail.myvolusionstore.com) as both your incoming and outgoing server, you will see delays in sending email over AT&T's system.
What AT&T appears to be doing is catching all mail traffic sent over TCP port 25 (the default SMTP port) and forcing it to be rerouted through their SMTP server. This is likely done to allow AT&T to monitor all outgoing mail traffic in order to track spam, etc. This rerouting is what causes the send mail delay.
Note for Verizon Users
As of February 2009, Verizon Communications has begun to require POP email client users to update their send mail (SMTP) port settings to 587 from the standard, port 25. If you're using Verizon's ISP services, you should take this change into account in regards to your store's POP email settings.