To set an alternate SMTP port in Microsoft Outlook Express:

1. In Microsoft Outlook Express  go to Tools > Accounts
2. Click the Mail tab.
3. Click the account and then click Properties.
4. Click the Advanced tab
5. Change “Outgoing mail (SMTP)“. The alternate port will be provided to you by your host, which is generally 25 or 587
6. Click Apply and then OK.

To set an alternate SMTP port in Mozilla Thunderbird:

1. In Mozilla Thunderbird go to Tools > Account Settings
2. Now, select “Outgoing Server (SMTP)” at the bottom of the list that you see in the left panel.
3. Select the account and click Edit
4. Change Port from 25. The alternate port will be provided to you by your host, which is generally 25 or 587.
5. Click OK.