Bond is trying to persuade Collins to include language from the House version of the measure that would allow ratepayers to challenge individual rates, such as the price of first class mail, if they do not see them as "fair and equitable."
Mailing industry lobbyists and a Senate aide said a coalition of large mailers was able to reach a consensus on the provision earlier this fall, but L.L. Bean, which is headquartered in Collins' home state of Maine, objected.
Postal lobbyists also noted that Hallmark, which relies on first class mail and is headquartered in Missouri, pushed Bond to put a hold on the bill unless a deal can be reached.
A spokeswoman for Collins and a spokesman for Bond said that while the hold remains in place, they will continue to discuss their differences.