SMTP Settings

Threads count - number of threads for simultaneous mailbox checkup.

Retries count - number of times the program will try to establish connection to mail server for mailbox checkup.

Custom HELO - domain name or IP address used to connect to mail server. Some servers demand this parameter is not empty and check this IP address is valid. You can set the correct IP-address automatically here.

Custom MAIL FROM - e-mail address sent to mail server as a parameter of MAIL FROM command. In theory this can be fake, however, some mail servers do analyze it. Thus it is not recommended to delete this parameter or use a fake address.

Common Settings
DNS Settings
Email Filters Settings