@LimitLess Please
download, extract and run MTADiag and follow the instructions.
Press 'n' when asked.
Post any Pastebin URL MTADiag gives you.
Well its called Connection bug to the server. It happens to me alot with some servers.
I just turn off my computer. then restart my internet router. Then Run MTA SA as adminstrator.
That works for me.
Try it up and tell me if it worked.