Khan, who knows Acts owner Irv Richter and helped arrange bringing the business to Camden, hosted the event, which drew thousands.
Richter, also chairman and CEO of Hill International, said that he had no knowledge of the e-mail and that all hires would be based on capability.
Khan described the e-mail, which he said he did not authorize his campaign to send, as poorly worded. He acknowledged that job applicants were invited to volunteer but said there was never a quid pro quo.
"Do we want them to register? Absolutely. Do we want them to vote for us? Absolutely," Khan said. "Was it strategic to have this prior to the election? Absolutely. Do we want anybody to be pressured or feel it's a prerequisite? Absolutely not."
On Monday, volunteers, some of whom had received the e-mail, arrived at 11 a.m. to get T-shirts. They circulated around the crowd with voter registration forms.
The event showed the desire for jobs in Camden, where the unemployment rate is 19 percent. More than 5,000 applications were turned in by the end of the rally, organizers said.
Khan said the preapplication forms were set up in anticipation of a large crowd. He said that 602 people completed them and that those people would be called first for interviews regardless of whether they volunteered with the campaign.
The e-mail offers people a "last chance" to sign up to volunteer and concludes with, "Remeber Your Initiative and Support Will Determine Your Future!"
Richter said he had nothing to do with the e-mail.
"I don't care who they vote for. I don't even care if they made a mistake in their background," said Richter, who said he was open to hiring ex-convicts. "We want the most qualified people. I'm trying to run a business. He's trying to run a campaign."
Khan does not own any part of the company and has no say in hiring practices, Richter said.
Joseph Donohue, deputy director at the New Jersey Election Law Enforcement Commission, said the e-mail did not appear to violate campaign-finance laws.