Q: I learned that e-mail providers sometimes block mail sent from other providers over the issue of misuse. But when my provider was blocked, I wasn't told. I only learned later that some of my outgoing mail wasn't delivered. Shouldn't e-mail users be notified if they're being blocked?

Dutch Nagle, Hereford, Ariz.

A: The deliberate blocking of e-mail traffic is an anti-spam (junk mail) defense. While it inconveniences some e-mail users, it's also fleeting, so users are unlikely to be notified.

Why does it happen at all? When e-mail provider A receives an excessive amount of spam from provider B, A blocks incoming mail from B. This isn't punishment so much as a wake-up call to provider B to get rid of the spammers using its e-mail network. Once B takes action against the spammers, A lifts its blockade, usually in a couple of days. Among e-mail providers, this is considered to be responsible spam-prevention, so it's likely to continue.

Fewer consumers are affected than you would think. Why? Because e-mail provider A doesn't usually block all mail coming from provider B, just the mail coming from a few of B's mail servers — the ones used by the spammers. So only some of provider B's customers are blocked.

But if you feel your e-mail provider is being blocked too frequently — signifying a poor job of policing for spammers — change providers.

Q: My Microsoft Word documents have all been mysteriously changed to something called "Office Open XML Documents." Now Word can open but not edit them. What's wrong?

Ron Atkinson, Bloomington

A: You are the victim of a mass-file conversion, but you can undo it.

Your files have been converted from the pre-Office 2007 Word file format (.doc) to the newer file format (.docx). The latter format is also called "Open XML."

If you are using a pre-Office 2007 version of Word, it can't open .docx files without some help.

At the time Office 2007 was introduced, Microsoft provided that help in the form of a downloadable (but now discontinued) program called Office Compatibility Pack. It enabled pre-2007 copies of Word to at least open .docx files. Because you can open .docx files, I suspect that you're using Compatibility Pack right now.

However, another feature of Compatibility Pack enabled it, in conjunction with Microsoft's Office File Converter, to turn all .doc files to .docx files. That may have happened to you.

To convert your .docx files back to .doc files for free (but one at a time), use online services Convertio (see tinyurl.com/y4yllkty) or Onlineconvertfree (see tinyurl.com/y3u9xy8e). Convertio also offers bulk file conversion for a fee.

Q: I'm getting unwanted robocalls, and I don't know how to block them with my CenturyLink landline phone. Is there anything I can do?

Susan Van Cleaf, Plymouth

A: CenturyLink offers a "call rejection" service that blocks up to 25 phone numbers on a landline phone (see tinyurl.com/y5gynw6e). Each time you get a robocall, add that number to your blocked list. You will probably be rid of the robocalls long before you get to 25 numbers.

E-mail tech questions to steve.j.alexander@gmail.com. Include name, city and telephone number.