I am using Seamonkey to handle several mail accounts, some @verizon.net, others at my own domains (via Godaddy).
The Godaddy accounts are fine, but the Verizon accounts will receive but cannot send. They used to send, too (albeit with occasional glitches) but Verizon apparently changed something in its system a few months ago and now they don't.
I have tried the following outgoing server settings:
using my default server (GoDaddy's) -- doesn't work.
Using outgoing.verizon.net with port set to 465, to 995m to 25, and to 110 -- no outgoing with any (currently set to port 465)
Tried Connection Security as "None" and as "SSL/TLS"--AFAIK I have used both settings with each of the port settings above.
Authentication method set as Normal password
Full account address given as User Name.
Incoming settings (which work) are: Incoming.verizon.net, port 110, Connection Security none, Authentication Method Password Transmitted insecurely.