I'm with Rogers, and I've been running Mercury with a different port for years (I use a number in the 20,000 range) on MercuryS.  But I do use MercuryC SMTP client and MercuryD 

POP3 client and let Rogers forward all my emails -- partially because they don't allow static IP addresses.  I use EasyDNS to have all my email addresses forwarded to my rogers address.  Every 30 seconds my POP3 client picks up the mail from Rogers and distributes internally.  My email clients send to MercuryS on the funny port, and then the SMTP client forwards that to Rogers, which in turn sends it to wherever.  Hope this helps.

Hi team:

 I'm new to the world of email servers, but figured I'd try my hand at it.  I'm able to receive email to my account from external accounts.  I am also able to send email to myself and receive it, however, I am NOT able to send emails to outgoing accounts unless I use MercuryC instead of MercuryE (which isn't very practical).

I'm with Rogers ISP in Canada, I'm not sure if they're blocking port 25 or what the beef is, but if I change the settings for MercE from 25 to another random port, would that be enough to get around the ISP Blacklist (if that is the cause of the problem)?

Thanks guys,

Richard 

Mail servers use port 25 to communicate with each other, so another port won't do I'm afraid. If you have a fixed IP address you could ask your ISP to allow port 25 for you, but many ISPs aren't very flexible with such things so MercuryC may be the only solution.

/Rolf 

Thanks Rolf!

[edit]

Just spoke to Rogers support - they have confirmed (as I was afraid of) that they do have port 25 blocked.

Do you guys have a list up of ISP's that have the port blacklisted?  It might be a handy quick resource. 

I just ran into this problem with traveling salespeople at two separate locations.  I finally solved the problem by activating alternate port 587 in the Mercury SMTP server, and routing that port to our mail server.  The clients just had to change their SMTP port to 587 and the problem went away.