Hi and welcome.
I have been using Secureline for awhile now and have no issues with sending or receiving emails. I use Thunderbird.
When I first started using I did have a glitch with mail not working properly, but that was because the (web based)Email: gmail, msn and yahoo didn’t Recognize the IP that was making the request (obviously while connected to Secureline your IP is different) so I had to go online while connected and sign in manually before Thunderbird could receive mail from these web based email addresses.;
Not sure if this applies as I am not knowledgeable with you Email setup/provider etc. 