eClient won't send of receive message. Error.

I set up eM Client in a few months ago. My daughter and myself are the only two people who will be using the account. I attempted 8 times today to send her a message with no success.

I just keep getting this message: 5.3.4 554-554 5.2.0 STOREDRV.Deliver; delivery result banner

No settings were changed by her or myself.

Any ideas what has caused this. It is up to date.

All help is appreciated.
Let me know if you need any further information.

Hello Sande,

Could you please log into your e-mail through webmail and see if your provider sent you a message with a request for account verification? Sometimes providers block access from third party apps and you need to provide certain information/verify that the attempt at connection comes from you.
Let us know if it helped.

Regards,
Maurice

I checked my account both inbox and spam and there was never a message from them concerning this. And I had been using the account with no issue and then suddenly this stated. I think it started when what I had to verify that I wanted a free account or paid. I verified that I wanted free and entered whatever other information they wanted and the issue started then. 

Sorry but I decided to uninstall it. I just didn’t need the hassle.

Hello Sande,

We’re sorry to hear you decided to uninstall eM Client. This problem however couldn’t be influenced by the type of your license. If you decide to give it another go, we’ll be happy to provide more assistance.

Regards,
Maurice