I am a junior partner in a law firm, promoted less than a year ago. My promotion was very much supported and "sponsored" by a much more senior partner (X) for whom I had worked for years. He and I have a common Department Head (Big Boss).
The other day Big Boss suggested to me that X should be giving me more official credit in the firm' figures for work I do for a very large client (Big Client) that X originally introduced. I said that I knew, understood and accepted why X could not do that. Big Boss suggested that X should do so for the greater good of our Dept.
Yesterday (Sat) about lunchtime I received a multi-page ranting email from X accusing me of claiming to Big Boss that Big Client sends the vast majority of its new work to me and not X (I did not claim this as it is not true), how dare I demand that he hand over a slice of his hard-won practice to me, he's built it up over many years and I am waltzing in trying to take over, he takes all sorts of shit for me so that I don't get overwhelmed as a new partner, who do I think I am, he doesn't sleep nights for worrying about his files and clients and I have it easy, I have been saying things to clients that suggest he and I are fighting about credit for work - it goes on and on and on, ending hilariously with 'but don't think I don't appreciate what you do". I have never done or said any of these things, I frequently thank X for his support and I see myself very much as his trusted deputy. I enjoy being a partner but I am not rabidly ambitious and have no intention of usurping X who is only a few years older than me. I plan to sod off on maternity leave within about a year and probably come back part time, if at all.
X is known to be something of a paranoid worrier (part of the reason why the other partners in our Dept thought that promoting me to support him was a good idea). I normally get on pretty well with him. Big Boss, who I phoned immediately on the verge of tears, is adamant that he did not tell X that I was pushing for credit. Frankly, X's email comes across as unhinged. I am horrified that he has jumped to conclusions and not given me the benefit of the doubt, particularly as Big Boss is well known to have his own agenda whereas I am the least political player ever and X should, if he knows me at all, realise this. I am shocked that X felt the need to send a ranting email at the weekend instead of just talking to me on Monday - he's an experienced manager and should know much better than this. I haven't replied to X or forwarded the email to anyone else. I intend to have a meeting with X first thing on Monday morning. So the question is do I bother to engage in a point by point rebuttal of everything X accused me of, or do I express concern for his mental health? And how do we move forward from this?