can I stop guest use of email

[joehark]

My error log tells me my two week old, low traffic SM site is being hit a number of time per minute, 24/7 by "guests" who are trying to use mail but generate a 535 error.

Obviously, these attempts are from people who want to send out spam. I have mail turned off for guests. And their attempt generates the errors message.

When I visit the site without being logged in, I do not see any way for a guest to even start a email. How are they able to even see and start email?

Wherever that access may be, how can I block guests from even seeing it? I am sure I am not the only one who has this issue but I did not find a mod or a post here in the forum to deal with it.

Suggestions please? 

[Kindred]

https://wiki.simplemachines.org/smf/SMF2.0:Security_and_Moderation
Do not reveal contact details of members to guests - If selected, this option will hide the e-mail addresses and messenger contact details of all members from any guests on your forum
Allow viewable email addresses - If this option is enabled instead of users e-mail addresses being hidden to normal members and guests they will be publicly viewable on the forum. Enabling this will put your users at greater risk of being victims of spam as a result of e-mail harvesters visiting your forum. Note: this setting does not override the user setting for hiding their email address from users. Enabling this setting is not recommended.

[joehark]

Thanks for the response. I have had the following setting since I published the board

Do not reveal contact details of members to guests - checked
Allow viewable email addresses - not checked

But still I am see Guest attempts to use mail and generating Error 535. I've received more than a dozen while writing this message.

Here's the full merrr message

Apply Filter: Only show the error messages of this URL
http://mywebsite.com/index.php?scheduled=mailq;ts=1525984596
Apply Filter: Only show the errors with the same message
Ran into problems sending Mail. Error: 535 Incorrect authentication data

So, with sincere respect, something else is going on. How can these would be hackers even attempt to send email. When I am logged out and come to the board as a Guest, I cannot find anything that looks like a way to send email. But they are finding something. Does anyone know how that is possible?

[Illori]

that means the guest is hitting the forum casusing a scheduled task to run that needs to send email. the email is not able to authorize to the server.

[joehark]

are you saying that this is happening automatically when a guest vis1ts the forum and is not something someone is doing maliciously?

[Illori]

correct

[joehark]

so, either this is happening to everyone (which I doubt) or there is a setting that is causing it. Do you have a suggestion as to where that setting might be?

[a10]

Does normal email sending \ queue (pm notifications, registration emails etc) work correctly ?

[Aleksi "Lex" Kilpinen]

so, either this is happening to everyone (which I doubt) or there is a setting that is causing it. Do you have a suggestion as to where that setting might be?

Do test your mail functionality. Send a newsletter to yourself, try notifications, run the scheduled task manually. The error is one that would either happen to everyone always, or be a temporary login issue in mail service connectivity.