Email was running fine in Manager io. But today appearing an error as mentioned in screenshot. Any one can guide me.
Read this Guide: Troubleshoot email issues | Manager. Visit all relevant links it contains. If that does not solve your problem, provide all the information specified in the Guide.
I suffered several times from a “working” implementation to one that stopped working. Every time it was not Manager but my VPS or another provider. So look if “server edition” if the hosting provider blocks SMTP to 3rd parties. When the desktop version checks your firewall and allows Manager mails.
Issue resolved.