07: Where can I drop off my mail-in ballot in person within Kent County in Delaware?

According to the Delaware Secretary of State, you may return your absentee ballot to the Department of Elections office in your county:

Kent County Department of Elections: 100 Enterprise Pl Ste 5, Dover DE 19904 (source)

Phone: (302) 739-4498
Email (Absentee Voting): absenteekc@delaware.gov
Email (Vote By Mail): votebymailkc@delaware.gov

07: Where can I drop off my mail-in ballot in person within New Castle County in Delaware?

According to the Delaware Secretary of State, you may return your absentee ballot to the Department of Elections office in your county:

New Castle County Department of Elections: Carvel State Office Building, 820 North French St Suite 400, Wilmington DE 19801 (source)

Phone: (302) 577-3464
Email (Absentee Voting): absentee@delaware.gov
Email (Vote By Mail): votebymailncc@delaware.gov

07: Where can I drop off my mail-in ballot in person within Sussex County in Delaware?

According to the Delaware Secretary of State, you may return your absentee ballot to the Department of Elections office in your county:

Sussex County Department of Elections: 119 N. Race St, Georgetown DE 19947 (source)

Phone: (302) 856-5367
Email (Absentee Voting): absenteesc@delaware.gov
Email (Vote By Mail): votebymailsc@delaware.gov