Very likely the Emailplus plugin is not fully compatible with Elgg 2 yet. While I see that around line 255 there's some indication of support for Elgg 2 the error seems to be caused by the necessary Elgg 2 message class not being available.

It might help to add a line

use Zend\Mail\Message;

at the top of the file emailplus/lib/emailplus.php. But without using and testing this myself I can't say for sure. And there might be other issues with using the Emailplugin plugin on Elgg 2. Maybe it helps to notify the plugin developer about the issue and ask for help / an updated version.

Thank you for your reply

Make sure your PHP environment can send mail (Google and StackOverflow can help here). On the other end, ask the recipient to check his/her spam folder.

I have got the same problem. My guess: One has to install DKIM and SPF to validate, look also: https://support.google.com/mail/answer/180707?hl=en

without DKIM (DMARC) And SPF many email hosts will either reject or junk any mails you send, yes. ideally you also need to test whether your server is actually sending any mails at all. how you check that will depend on whether you are running your own email server or not.

Did you these recommendations?

I thank RvR flush the caches but continues all the same, the migration of the product is correct then you can appreciate entering: www.socialgame3g.com

?thank you very much Daniel