LOGGING on to Gmail or other e-mail service has become a routine of daily life, completed without a thought. What would you do, however, if you woke up tomorrow, plugged in your user name and password as you always do, but then received an unfamiliar message: “User name and password do not match”?

If you’re a Gmail user, what you’ll want to do after a few more unsuccessful, increasingly frantic attempts is to speak with a Google customer support representative, post haste. But that’s not an option. Google doesn’t offer a toll-free number and a live person to resolve the ordinary user’s problems.

Discussion forums abound with tales of woe from Gmail customers who have found themselves locked out of their account for days or even weeks. They were innocent victims of security measures, which automatically suspend access if someone tries unsuccessfully to log on repeatedly to an account. The customers express frustration that they can’t speak with anyone at Google after filling out the company’s online forms and waiting in vain for Google to restore access to their accounts.

Tom Lynch, a software entrepreneur who lives near Austin, Tex., discovered early last month that he had been locked out of both Gmail accounts he used; he had no idea why. He received boilerplate instructions for recovering his accounts that did not apply to his particular circumstances, which included his failing to maintain a non-Gmail e-mail account as a back-up. He said it took him four weeks, including the use of a business directory and talking with anyone he could find at Google, before he succeeded in having service restored.