Security Warning on Outlook 2013

[#1]

I've attached a screenshot of an Internet Security Warning I get on the first email I send after opening Outlook 2013 which says:

Internet Security Warning
The server you are connected to is using a security certificate that cannot be verified.
The target principal name is incorrect.
Do you want ot continue using this sever.

I answer Yes to continue and the email send successfully. Only on first email I send then I don't see it again on further emails until I shutdown and restart Outlook.

I've not changed anything for months but warning only appeared in the last few weeks. Same SMTP settings, going through my same plusnet router, same Win 10 PC, same Outlook 2013.

Any ideas?

[#2]

Hi @ashburnhamins 

Can you please click View Certificate and let us know what is shown within that dialog?

Thanks

[#3]

Hi @ashburnhamins,

Thanks for getting in touch.

I'm sorry to hear that, this will be associated with your mail settings in your Outlook programme. I've included a link here which seems to follow a common online approach to this issue:

Please bear in mind this is a third party site and the Outlook version was 2010,  I can't verify the advice given however the issue is the same from what I can see for most versions on Outlook from 2007 onward.

I hope this helps resolve the issue.

Thanks - LF

[#4]

@LordFoul this helped solve the problem. I was using Outgoing SMTP port 587 but the "Use the following type of encrypted connection" was set to "Auto". I've changed this to "None" and now the warning message is gone.

A little strange as Auto was working fine up until a few weeks ago but problem now solved so thanks for your help.

@Jon let me know if you still want the screenshot of certificate to assist you with anything but problem now solved my side.

[#5]

That's great to hear @ashburnhamins, it does seem to be a recurring issue on Outlook versions so I'm pleased the solution was effective.

Let us know if you need anything further.

Thanks - LF

[#6]

Hi @ashburnhamins 

That is probably not the ideal answer and certainly not a "fix" but it is avoidance / mitigation of the symptoms.  Try STARTTLS for the SMTP settings.

With OL2013 "Auto" works fine if there are no options supported … !!

This would only impact the first attempt to send, because after the first attempt / failure OL will fall back to "None".

[#7 · Accepted solution]

@Townman @LordFoul @Jon 

Found the real problem behind this... I was using the SMTP server smtp.plus.net which I can see does not match the security certificate which says relay.plus.net hence the warning I was receiving.

Seems I have been using old settings which have worked fine up until recently but upon updating my server to relay.plus.net, I can now use Auto again for my type of encrypted connection and now have no errors.

Thanks for you help guys, apologies I didn't spot this earlier but may help others that start receiving this warning.

[#8]

@ashburnhamins
Well done for picking up this problem
Supporting smtp.plus.net, etc on Security Certificates would need another set of server names.
The decision was taken to support relay.plus.net (along with equivalents for Force9 and Free Online) to minimise costs.