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Please note: This item is from our archives and was published in 2011. It is provided for historical reference. The content may be out of date and links may no longer function.
Q: I can receive email through Outlook, but I can no longer send email through Outlook. My POP3 email previously worked just fine, and I have not changed the password or any mail settings. What’s going on, and how do I fix this problem?
A: Based on your description, it is possible that your Internet service provider (or a relay service provider) has tagged you as a spammer and is therefore blocking your outgoing email. This is a common problem, particularly for those who send messages using email merge (because groups of merged email messages appear similar to spam activity).You may also be tagged as a spammer if your computer is infected with a virus that is secretly sending spam from your computer when it is idle. (This may be possible even if you are running antivirus software.)
Although this problem sounds bad, POP3 users can usually solve it by changing their outgoing port from 25 to 587, as follows:
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Outlook 2010: From the File tab, select Info, Account Settings, Account Settings (again) to open the Account Settings dialog box. Under the E-mail tab, select the email account that is not sending properly and click Change Account to open the Internet E-mail Settings dialog box. Click the More Settings button, and on the Advanced tab change the value in the Outgoing server (SMTP) box to 587 as shown below, and click OK, Next, Finish. Click the Close button to close the Account Settings dialog box.
Outlook 2007: From the File menu, select Data File Management to open the Account Settings dialog box. Under the E-mail tab, select the email account that is not sending properly and click Change to open the Internet E-mail Settings dialog box. Click the More Settings button, and on the Advanced tab change the value in the Outgoing server (SMTP) box to 587, and click OK, Next, Finish. Click the Close button to close the Account Settings dialog box.
Outlook 2003: From the Tools menu, select E-mail Accounts, and in the resulting dialog box select View or change existing e-mail accounts and click Next. Click the More Settings button, and on the Advanced tab change the value in the Outgoing server (SMTP) box to 587, and click OK.
This issue relates to the Internet Engineering Task Force (IETF) memorandum RFC 4409 “Message Submission for Mail,” a set of standards formalized in April 2006 to help fight spam. Among other measures, this memorandum mandates that, for all email messages sent via port 587, any alias names must be resolved when email is relayed from one server to the next, making it easier to trace the true source of email messages. Messages sent via port 25 are not required to abide by such standards, therefore many Internet service providers now block messages sent via port 25 for senders suspected of spamming. Upon changing your port setting, you should be able to once again send email.
Note: Companies using IMAP and Microsoft Exchange Server are also susceptible to this problem. In this case, the solution is the same, except changes to the outgoing port are made at the IMAP server, not at each user’s desktop.
The September Technology Q&A column shows how to create dynamic to-do lists with Excel's checkboxes and also how to set up multifactor authentication texts that don't rely on phones. Flip through both items and view a video walkthrough in our digital format.
