Can we assume that email from your PC works? Does the scanner have its own email address, or does it use yours?

If your modem is also a router (WiFi?) check that SMTP and POP3 ports are not blocked.

In case the ISP does something funny, try using port 25 or 465 instead of 587. Port 25 does not require TLS or authentication.

Thanks for your reply. Yes e-mail from the PC works fine. The scanner uses my (gmail) email address.

Yes the modem is also a WiFi router (KPN Experia V10).

I have tried port 25 and 465 a few times but no luck.

Will try to access the modem to see if there is any blocking of ports.

If the PC can send emails, then the router settings should be OK too.

Error <11> implies the SMTP server address is incorrect but "smtp.gmail.com" is correct as far as I know. Try re-entering it on the printer, in case something went wrong when you moved.

Better still, try a factory reset on the printer; that will clear any potential funnies. On the printer's control panel go to Settings > General Settings > Factory Defaults > Restore Now > Submit. More info is in the on-line manual - including the suggestion to print a config page first so you will remember all the settings.

Thank you for your help and reset suggestion.
I tried this 2 days ago and tried it again today but this reset did not clear any network settings.
However, under security I found three other options to restore; printersettings, networksettings or Apps.
Tried resetting networksettings first but that did not restore any smtp settings.
Tried resetting printersettings and that cleared most of the settings, incl the smtp settings.

Entered the gmail smtp settings from scratch but no luck on 587 or 465 ports
Get a "connection failure" immediately but the error code has changed from <-11> to <-51>.
Error <-51> "unable to get issuer certificate".

Under Certificate Management I have uploaded two certificates, received from Lexmark last year when I set up this printer for the first time.

Equifax_Aug_22_1998_To_Aug_22_2018
Thawte Premium Server CA_Aug__1_1996_To_Dec_31_2020

I deleted and installed but certificates and booted the printer but the error remains.

Should I update these certificates and if so, how?

I think the certificates should still be valid. I would start by trying port 25, to remove the requirement for SSL/TLS.

You can also go through the suggestions in Lexmark's secure email guide.

I used port 25 with the gmail settings, with and without SSL/TLS and verification but nothing worked.
Tried the same with my business smtp setting without success. Finally I entered my private (KPN) account smtp settings and was not expecting anything but surprisingly this seems to work.
Is there any danger in using these settings?

Bedankt voor de puntjes, JR.

Did the DNS change fix it?