Linus Server / Parallels Plesk Management

I have recently moved from a shared hosting to a virtual server (VS) hosting. The VS is with 1and1 hosting company. The entire transfer of files and database has been successful without any problems. The main issue I face is with the emails. a. All email accounts created on 1and1 panel works perfectly fine without any problems. Email can go out to different domains is received with no issues. b. Server generated (automated) emails is a problem. Server generates email such as forgot password email, or registration emails e.t.c. to different customers of mine and some emails to myself (of the same domain). Emails go successfully to different domains, but all emails sent to my domains which is hosted with 1and1 gets stuck. These emails can all be seen in mail queue in plesk. Customers whose domain are hosted with 1and1 also don't receive emails. I am thinking there is a slight process change on how it deals with emails internally I need someone to have a look at this.