3 K N O W N B U G S I N S E N D M A I L
6 The following are bugs or deficiencies in sendmail that we are aware of
7 but which have not been fixed in the current release. You probably
8 want to get the most up to date version of this from ftp.sendmail.org
9 in /pub/sendmail/KNOWNBUGS. For descriptions of bugs that have been
10 fixed, see the file RELEASE_NOTES (in the root directory of the sendmail
13 This list is not guaranteed to be complete.
15 * Header values which are too long may be truncated.
17 If a value of a structured header is longer than 256 (MAXNAME)
18 characters then it may be truncated during output. For example,
19 if a single address in the To: header is longer than 256 characters
20 then it will be truncated which may result in a syntactically
23 * Delivery to programs that generate too much output may cause problems
25 If e-mail is delivered to a program which generates too much
26 output, then sendmail may issue an error:
28 timeout waiting for input from local during Draining Input
30 Make sure that the program does not generate output beyond a
31 status message (corresponding to the exit status). This may
32 require a wrapper around the actual program to redirect output
35 Such a problem has been reported for bulk_mailer.
37 * Null bytes are not handled properly in headers.
39 Sendmail should handle full binary data. As it stands, it handles
40 all values in the body, but not 0x00 in the header. Changing
41 this would require a major restructuring of the code -- for
42 example, almost no C library support could be used to handle
45 * Header checks are not called if header value is too long or empty.
47 If the value of a header is longer than 1250 (MAXNAME + MAXATOM - 6)
48 characters or it contains a single word longer than 256 (MAXNAME)
49 characters then no header check is done even if one is configured for
52 * Header lines which are too long will be split incorrectly.
54 Header lines which are longer than 2045 characters will be split
55 but some characters might be lost. Fix: obey RFC (2)822 and do not
56 send lines that are longer than 1000 characters.
58 * milter communication fails if a single header is larger than 64K.
60 If a single header is larger than 64KB (which is not possible in the
61 default configuration) then it cannot be transferred in one block to
62 libmilter and hence the communication fails. This can be avoided by
63 increasing the constant MILTER_CHUNK_SIZE in
64 include/libmilter/mfdef.h and recompiling sendmail, libmilter, and
65 all (statically linked) milters (or by using an undocumented compile
66 time option: _FFR_MAXDATASIZE; you have to read the source code in
67 order to use this properly).
69 * Sender addresses whose domain part cause a temporary A record lookup
70 failure but have a valid MX record will be temporarily rejected in
71 the default configuration. Solution: fix the DNS at the sender side.
72 If that's not easy to achieve, possible workarounds are:
73 - add an entry to the access map:
75 - (only for advanced users) replace
77 # Resolve map (to check if a host exists in check_mail)
78 Kresolve host -a<OKR> -T<TEMP>
82 # Resolve map (to check if a host exists in check_mail)
83 Kcanon host -a<OKR> -T<TEMP>
84 Kdnsmx dns -R MX -a<OKR> -T<TEMP>
85 Kresolve sequence dnsmx canon
88 * Duplicate error messages.
90 Sometimes identical, duplicate error messages can be generated. As
91 near as I can tell, this is rare and relatively innocuous.
93 * Misleading error messages.
95 If an illegal address is specified on the command line together
96 with at least one valid address and PostmasterCopy is set, the
97 DSN does not contain the illegal address, but only the valid
100 * \231 considered harmful.
102 Header addresses that have the \231 character (and possibly others
103 in the range \201 - \237) behave in odd and usually unexpected ways.
105 * accept() problem on SVR4.
107 Apparently, the sendmail daemon loop (doing accept()s on the network)
108 can get into a weird state on SVR4; it starts logging ``SYSERR:
109 getrequests: accept: Protocol Error''. The workaround is to kill
110 and restart the sendmail daemon. We don't have an SVR4 system at
111 Berkeley that carries more than token mail load, so I can't validate
112 this. It is likely to be a glitch in the sockets emulation, since
113 "Protocol Error" is not possible error code with Berkeley TCP/IP.
115 I've also had someone report the message ``sendmail: accept:
116 SIOCGPGRP failed errno 22'' on an SVR4 system. This message is
117 not in the sendmail source code, so I assume it is also a bug
118 in the sockets emulation. (Errno 22 is EINVAL "Invalid Argument"
119 on all the systems I have available, including Solaris 2.x.)
120 Apparently, this problem is due to linking -lc before -lsocket;
121 if you are having this problem, check your Makefile.
123 * accept() problem on Linux.
125 The accept() in sendmail daemon loop can return ETIMEDOUT. An
126 error is reported to syslog:
128 Jun 9 17:14:12 hostname sendmail[207]: NOQUEUE: SYSERR(root):
129 getrequests: accept: Connection timed out
131 "Connection timed out" is not documented as a valid return from
132 accept(2) and this was believed to be a bug in the Linux kernel.
133 Later information from the Linux kernel group states that Linux
134 2.0 kernels follow RFC1122 while sendmail follows the original BSD
135 (now POSIX 1003.1g draft) specification. The 2.1.X and later kernels
136 will follow the POSIX draft.
138 * Excessive mailing list nesting can run out of file descriptors.
140 If you have a mailing list that includes lots of other mailing
141 lists, each of which has a separate owner, you can run out of
142 file descriptors. Each mailing list with a separate owner uses
143 one open file descriptor (prior to 8.6.6 it was three open
144 file descriptors per list). This is particularly egregious if
145 you have your connection cache set to be large.
147 * Connection caching breaks if you pass the port number as an argument.
149 If you have a definition such as:
151 Mport, P=[IPC], F=kmDFMuX, S=11/31, R=21,
152 M=2100000, T=DNS/RFC822/SMTP,
155 (i.e., where $h is the port number instead of the host name) the
156 connection caching code will break because it won't notice that
157 two messages addressed to different ports should use different
160 * ESMTP SIZE underestimates the size of a message
162 Sendmail makes no allowance for headers that it adds, nor does it
163 account for the SMTP on-the-wire \r\n expansion. It probably doesn't
164 allow for 8->7 bit MIME conversions either.
166 * Client ignores SIZE parameter.
168 When sendmail acts as client and the server specifies a limit
169 for the mail size, sendmail will ignore this and try to send the
170 mail anyway. The server will usually reject the MAIL command
171 which specifies the size of the message and hence this problem
174 * Paths to programs being executed and the mode of program files are
175 not checked. Essentially, the RunProgramInUnsafeDirPath and
176 RunWritableProgram bits in the DontBlameSendmail option are always
177 set. This is not a problem if your system is well managed (that is,
178 if binaries and system directories are mode 755 instead of something
181 * 8-bit data in GECOS field
183 If the GECOS (personal name) information in the passwd file contains
184 8-bit characters, those characters can be included in the message
185 header, which can cause problems when sending SMTP to hosts that
186 only accept 7-bit characters.
188 * 8->7 bit MIME conversion
190 When sendmail is doing 8->7 bit MIME conversions, and the message
191 contains certain MIME body types that cannot be converted to 7-bit,
192 sendmail will pass the message as 8-bit.
194 * 7->8 bit MIME conversion
196 If a message that is encoded as 7-bit MIME is converted to 8-bit and
197 that message when decoded is illegal (e.g., because of long lines or
198 illegal characters), sendmail can produce an illegal message.
200 * MIME encoded full name phrases in the From: header
202 If a full name phrase includes characters from MustQuoteChars, sendmail
203 will quote the entire full name phrase. If MustQuoteChars includes
204 characters which are not special characters according to STD 11 (RFC
205 822), this quotation can interfere with MIME encoded full name phrases.
206 By default, sendmail includes the single quote character (') in
207 MustQuoteChars even though it is not listed as a special character in
210 * bestmx map with -z flag truncates the list of MX hosts
212 A bestmx map configured with the -z flag will truncate the list
213 of MX hosts. This prevents creation of strings which are too
214 long for ruleset parsing. This can have an adverse effect on the
215 relay_based_on_MX feature.
217 * Saving to ~sender/dead.letter fails if su'ed to root
219 If ErrorMode is set to print and an error in sending mail occurs,
220 the normal action is to print a message to the screen and append
221 the message to a dead.letter file in the sender's home directory.
222 In the case where the sender is using su to act as root, the file
223 safety checks prevent sendmail from saving the dead.letter file
224 because the sender's uid and the current real uid do not match.
226 * Berkeley DB 2.X race condition with fcntl() locking
228 There is a race condition for Berkeley DB 2.X databases on
229 operating systems which use fcntl() style locking, such as
230 Solaris. Sendmail locks the map before calling db_open() to
231 prevent others from modifying the map while it is being opened.
232 Unfortunately, Berkeley DB opens the map, closes it, and then
233 reopens it. fcntl() locking drops the lock when any file
234 descriptor pointing to the file is closed, even if it is a
235 different file descriptor than the one used to initially lock
236 the file. As a result there is a possibility that entries in a
237 map might not be found during a map rebuild. As a workaround,
238 you can use makemap to build a map with a new name and then
239 "mv" the new db file to replace the old one.
241 Sleepycat Software has added code to avoid this race condition to
242 Berkeley DB versions after 2.7.5.
244 * File open timeouts not available on hard mounted NFS file systems
246 Since SIGALRM does not interrupt an RPC call for hard mounted
247 NFS file systems, it is impossible to implement a timeout on a file
248 open operation. Therefore, while the NFS server is not responding,
249 attempts to open a file on that server will hang. Systems with
250 local mail delivery and NFS hard mounted home directories should be
251 avoided, as attempts to open the forward files could hang.
253 * Race condition for delivery to set-user-ID files
255 Sendmail will deliver to a fail if the file is owned by the DefaultUser
256 or has the set-user-ID bit set. Unfortunately, some systems clear that bit
257 when a file is modified. Sendmail compensates by resetting the file mode
258 back to it's original settings. Unfortunately, there's still a
259 permission failure race as sendmail checks the permissions before locking
260 the file. This is unavoidable as sendmail must verify the file is safe
261 to open before opening it. A file can not be locked until it is open.
263 * MAIL_HUB always takes precedence over LOCAL_RELAY
265 Despite the information in the documentation, MAIL_HUB ($H) will always
266 be used if set instead of LOCAL_RELAY ($R). This will be fixed in a
269 $Revision: 8.61 $, Last updated $Date: 2011/04/07 17:48:23 $