Itsumo osewa ni natte orimasu (いつもお世話になっております): thank you, as always, for your help. The standard opening of an email to a client, followed by the writer’s company and name.
Gobusata shite orimasu (ご無沙汰しております): I have long failed to be in touch. A business guide advises this opening instead of the usual one when some time has passed without contact.