tcsh or mail hang?

[Anton Shterenlikht]

Last couple of months or so I occasionally 
get apparent hangs in mail(1)
on sending mail, i.e. after hitting CTRL/D.

The system was 10.3 and now is 11.0.

I use mail(1) interactively in tcsh(1), connecting
via ssh. The host is active, and I can always login
via a new ssh connection. When I do login via a separate
ssh connection, I see no mail process in top or ps -axwwdd, e.g.:

27486  -  Is        0:00.02 | |-- sshd: mexas [priv] (sshd)
27488  -  I         0:00.32 | | `-- sshd: mexas at pts/0 (sshd)
27489  0  Is+       0:00.10 | |   `-- -tcsh (tcsh)
28149  -  Is        0:00.02 | |-- sshd: mexas [priv] (sshd)
28151  -  I         0:16.19 | | `-- sshd: mexas at pts/1 (sshd)
28152  1  Is        0:00.03 | |   `-- -tcsh (tcsh)
28158  1  I+        0:24.27 | |     `-- ssh -Y <...> 

While I'm blaming mail(1), the problem might be in tcsh(1)
or ssh connection, or some rare combination of all three.

Has anybody else seen this?

Thanks

Anton