I will be travelling solo in June from Sicily to Greece and I am wondering if anyone has travelled overland (train, bus?) from Messina to the ferry port at Bari (Ferry to Igoumenitsa). Thanks

There is no easy way to do this journey. The only through train from the Straits of Messina to Bari is the overnight train which has no sleeping accommodation. By day, it's a whole day's journey with various changes.
I'd suggest an overnight train or ship from Sicily to Napoli, then a journey by train and/or bus to Bari to connect with an overnight ship to Igoumenitsa.

If going to Naples, you might as well just fly from there (Aegean?) to Athens. It would save time.

Thanks for your replies. I think the Naples / Bari option sounds best.