Retrieving email from old IMAP server fails with IO::Socket::IP error

Runbox 7 Runbox 7 Webmail
#1

I’m trying to setup some family members with RunBox sub-accounts and I am hitting some issues with retrieving and migrating over their emails from old IMAP servers.

They are trying to access an IMAP mailbox from a typical Linux server running Plesk. Connecting on port 993, with SSL/TLS, but attempts return this error:

DEBUG: …5.22/IO/Socket.pm:48: local error: IO::Socket::IP configuration failed

Any ideas?
FWIW we can access these mail boxes absolutely fine using other clients like Thunderbird, MacMail etc.

Thanks!