The offender would be liable to be punished and/or pay compensation under Section 43 read with Section 66 of the Information Technology Act. The relevant provisions applicable to your case should be Section 43, sub-sections (a), (b), (i) and (j), as follows:
43. Penalty and compensation for damage to computer, computer system, etc. -If any person without permission of the owner or any other person who is incharge of a computer, computer system or computer network,-
(a) accesses or secures access to such computer, computer system or computer network or computer resource;
(b) downloads, copies or extracts any data, computer data base or information from such computer, computer system or computer network including information or data held or stored in any removable storage medium;
(i) destroys, deletes or alters any information residing in a computer resource or diminishes its value or utility or affects it injuriously by any means;
(j) steal, conceals, destroys or alters or causes any person to steal, conceal, destroy or alter any computer source code used for a computer resource with an intention to cause damage;
he shall be liable to pay damages by way of compensation to the person so affected.
Complaint under Section 43 has to be made before the Adjudicating Officer appointed by your State Government under the IT Act.
Section 66 prescribes the punishment for the actions spelt out in Section 43:
66. Computer related offences. -If any person, dishonestly or fraudulently, does any act referred to in section 43, he shall be punishable with imprisonment for a term which may extend to three years or with fine which may extend to five lakh rupees or with both.
Subject to correction, I think since the IT Act itself does not specify the trial of offences, CrPC should be applicable and the offence should be cognizable and non-bailable. A case by the name of Kumar vs. Whiteley seems to come closest to your facts (couldn't find the full decision and this following case summary is from another website).
Kumar vs. Whiteley: In this case the accused gained unauthorized access to the Joint Academic Network (JANET) and deleted, added files and changed the passwords to deny access to the authorized users. Investigations had revealed that Kumar was logging on to the BSNL broadband Internet connection as if he was the authorized genuine user and ‘made alteration in the computer database pertaining to broadband Internet user accounts’ of the subscribers. The CBI had registered a cyber crime case against Kumar and carried out investigations on the basis of a complaint by the Press Information Bureau, Chennai, which detected theunauthorized use of broadband Internet. The complaint also stated that the subscribers had incurred a loss of Rs 38,248 due to Kumar’s wrongful act. He used to ‘hack’ sites from Bangalore, Chennai and other cities too, they said. The Additional Chief Metropolitan Magistrate, Egmore, Chennai, sentenced N G Arun Kumar, the techie from Bangalore to undergo a rigorous imprisonment for one year with a fine of Rs 5,000 under section 420 IPC (cheating) and Section 66 of IT Act (Computer related Offence).
But I won't raise your hopes. Even the most developed nations are still struggling with information technology law concepts such as limits of authorization, excess of authorization and standards of proof etc. For instance, in your case, the IT Act requires the action to be without the permission of the owner of the computer system or computer network; you are the owner of your email ID, but are you "owner of the computer system" on which the email's were residing and from which they were deleted - I think no, unless you were running your own mailserver. Even so, no harm in making a complaint to bring things on record and trying.