Emails send from some of the addresses in one domain are marked as spam by multiple email clients. Since just few addresses within the domain are marked as spam, I do not think it is a domain problem, or can it be?  I checked the email header, but do not have any experience with this and I don't know what to do next:  Thunderbird  X-Spam-Flag: YES X-Spam-Score: 6.63 X-Spam-Level: ****** X-Spam-Status: Yes, score=6.63 tagged_above=-10 required=5     tests=[ALL_TRUSTED=-1, BAYES_00=-1.9, DNS_FROM_AHBL_RHSBL=2.699,     HTML_MESSAGE=0.001, RCVD_IN_PBL=3.335, RCVD_IN_RP_RNBL=1.31,     RCVD_IN_SORBS_DUL=0.001, RDNS_NONE=0.793,     SHORT_HELO_AND_INLINE_IMAGE=1.39, URIBL_BLOCKED=0.001] autolearn=no   Yahoo  X-YahooFilteredBulk: 217.11.253.114  Received-SPF: none (domain of "ourdomain" does not designate permitted sender hosts)
This is a  about how to handle email sent from your server being misclassified as spam.  For additional information you may find these similar questions helpful:                    Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).  Now I want to know what should be done to create "good" emails. I know about reverse lookup etc., but (for example), what about a unsubscribe link with an unique ID?  Does that increase a spam rating?
What exactly happens when a Weeping Angel is quantum locked? What are Vertex and Pixel shaders? Find all $n\in\mathbb N^+$ such that the sum of the digits of $5^n$ is equal to $2^n$.   I've solved this, but I think the proof is a bit weird and I wonder if there's a better one.    My proof:  We can see that $n\neq 1$, $n\neq 2$, $n=3$, $n\neq 4$ and $n\neq 5$.  Let $n&gt;5$. Notice that $5^6$ has $5$ digits, while $\frac{2^6}{9}=7\frac{1}{9}$, so $5^6$ has to have at least $8$ digits in order for the sum of the digits to be able to at least reach $2^6$.  Everytime $1$ is added to the exponent of $5$, the amount of digits $5^n$ gets is at most $1$, while $\frac{2^{n+1}}{9}-\frac{2^n}{9}=\frac{2^n}{9}&gt;3$, so the lowest amount of digits it has to have to reach $2^n$ becomes higher by at least $4$.  When $n=6$, the amount of digits $5^n$ has is already lower than the amount it has to have in order to reach $2^n$, and I've just proved that the amount it has to have in order to reach $2^n$ grows faster than the amount of digits $5^n$ has, therefore $5^n$ will never be able to reach $2^n$ when $n&gt;5$.  Hence the only solution is $n=3$. Books for starting with analysis I am interested in self-studying real analysis, and I was wondering which textbook I should pick up. I know all high school mathematics, I have read  (I did most of the exercises).  I have completed a computational calculus course which covered everything up to and including integration by parts (including the substitution method and Riemann sums) I am currently considering:    From what I have heard this is not very well suited for self-study and that while the exercises are extremely difficult, if you take the time they are worth the effort.    I have heard that while Spivak explains proofs in much more detail than Principles, it doesn't cover all of the material in the latter.    I don't know much about this. I have only seen some comments saying that it is an excellent introduction to analysis.    Extra clarification edit: I would prefer a book not to ''dumb down'' the material, something that would not hold my hand through every step, something that would force me to fill in the gaps myself instead of explaining every single step. That is why I am currently leaning towards Rudin, but before I decide I would still like some information on the book by Apostol. Can a sum of a finite number of square roots of integers be an integer? If yes can a sum of two square roots of integers be an integer?  The square roots need to be irrational. The process substitution &lt;(cat) doesn't work. Why?  head &lt;(cat)  cat: -: Input/output error   I can use an extra file descriptor, but I don't understand why the above doesn't work.  # Using file descriptor 3 to reroute the input (head &lt;(cat &lt;&amp;3)) 3&lt;&amp;0 Create a bootable USB on a Mac to install Ubuntu on a PC How do I make multiple spawn points in minecraft vanilla? How to use numpad / on a keyboard without a numpad? I've just got into Blender, and I like it a lot. But as I just switched from a stationary computer to a MacBook, I've got some new problems regarding the numpad. I can use 1-9 perfectly, But I have no idea how to emulate buttons like / (used to enter local view). I've searched the web for an answer, but I can't find any. $$\int_{-\infty}^{\infty} \frac{\cos(αx)}{(x^2+1)(x^2+4)} \mathrm dx. $$  I am not sure how to solve this question. Can anyone help me to approach this problem. Thanks. Python: Find a substring in a string and returning the index of the substring Proving an alternating Euler sum: $\sum_{k=1}^{\infty} \frac{(-1)^{k+1} H_k}{k} = \frac{1}{2} \zeta(2) - \frac{1}{2} \log^2 2$ Let $$A(p,q) = \sum_{k=1}^{\infty} \frac{(-1)^{k+1}H^{(p)}_k}{k^q},$$ where $H^{(p)}_n = \sum_{i=1}^n i^{-p}$, the $n$th $p$-harmonic number.  The $A(p,q)$'s are known as alternating .     Can someone provide a nice proof that    $$A(1,1) = \sum_{k=1}^{\infty} \frac{(-1)^{k+1} H_k}{k} = \frac{1}{2} \zeta(2) - \frac{1}{2} \log^2 2?$$   I worked for a while on this today but was unsuccessful.  Summation by parts, swapping the order of summation, and approximating $H_k$ by $\log k$ were my best ideas, but I could not get any of them to work.  (Perhaps someone else can?)  I would like a nice proof in order to complete .  Bonus points for proving $A(1,2) = \frac{5}{8} \zeta(3)$ and $A(2,1) =  \zeta(3) - \frac{1}{2}\zeta(2) \log 2$, as those are the other two alternating Euler sums needed to complete my answer.   Added: I'm going to change the accepted answer to robjohn's $A(1,1)$ calculation as a proxy for the three answers he gave here.  Notwithstanding the other great answers (especially the currently most-upvoted one, the one I first accepted), robjohn's approach is the one I was originally trying.  I am pleased to see that it can be used to do the $A(1,1)$, $A(1,2)$, and $A(2,1)$ derivations. Are "pushforward" and "pullback by zero section" of diffrentials isomorphic in elliptic curves? Let S be a scheme, $p:E\rightarrow S$ be an elliptic curve with zero section $e:S\rightarrow E$. My question is: Are $p_*(\Omega_{E/S}^1)$ and $e^*(\Omega_{E/S}^1)$ isomorphic? I think it's right because I saw both definitions in different notes and they seem to represent the same thing. Thank you! What is $1^k+2^k+\cdots+ (p-1)^k$ modulo $p$? (From Ireland and Rosen). I've been working through a bit of Ireland and Rosen's Number Theory for fun. Problem 4.11 of Ireland and Rosen asks     Prove that $1^k+2^k+\cdots+(p-1)^k\equiv 0\pmod{p}$ if $p-1\nmid k$, and $-1\pmod{p}$ if $p-1\mid k$.    My work is leading where I didn't expect to go. Here I assume $p$ id odd. First, if $p-1\mid k$, then we can wrike $k=(p-1)j$ for some $j$. But then $$ 1^k+\cdots+(p-1)^k\equiv 1^{(p-1)j}+\cdots+(p-1)^{(p-1)j}\equiv \underbrace{1+\cdots+1}_{p-1\text{ times}}=\frac{(p-1)p}{2}\equiv 0\pmod{p} $$ since $p-1$ is even.   Secondly, I suppose $p-1\nmid k$. WLOG, I can assume $0&lt;k&lt;p-1$, Since if $k=(p-1)j+r$ with $0&lt;r&lt;p-1$, then  $$ a^k\equiv a^{(p-1)j+r}\equiv a^r\pmod{p}. $$  Then if $g$ is a primitive root, $$ 1^k+\cdots+(p-1)^k=\sum_{i=1}^{p-1}(g^k)^i=\frac{g^k(1-g^{k(p-1)})}{1-g^k}. $$ Since $g$ is primitive, $p\nmid 1-g^k$, but $p\mid 1-g^{k(p-1)}$, so the above sum is again congruent to $0\pmod{p}$.  So in all cases, I get the sum is congruent to $0$ regardless. Have I messed up, or is there a typo? Thanks. Generate random numbers uniformly over an entire range I am having a hard time with the following real analysis qual problem.  Any help would be awesome.  Suppose that $f \in L^p(\mathbb{R})$, where $1\leq p&lt; + \infty$. Let $T_r(f)(t)=f(t−r)$. Show that $\lim_{r \to 0} \|T_rf−f\|_{L_p} =0$, that is $$ \lim_{r\to 0} \left( \int_{\mathbb R} |f(t-r) - f(t)|^p \mathrm d t\right)^{1/p} =0.$$ Android App sometimes loses answer drafts I am trying to under stand how to build a barrel shifter using multiplexers. I understand how the barrel shifter works but I don't get how you decide the number of multiplexers to use, and how the shifting is done with the multiplexer basically.  So far wikipedia doen't help much. And the best I have so far is   But it does not really answer my question. How to create a hole in a polygon in QGIS? I'm trying to use the tool "delete ring" in order to create a hole in a polygon. The geometry of the hole is another feature of the same shapefile   I cannot manage to delete the part of the polygone. Does someone have a tutorial or some explanation? Allow [tag:tag-name] syntax to link to any site The tag  and meta-tag  syntax generate much nicer looking results than merely surrounding your tag with [square brackets].    However, they only work when you're talking about the site you're on.  On Area51, in Chat, and on Meta sites, this is frequently not the case, leading to attempts at syntax like [[tag:failure]](https://superuser.com/questions/tagged/failure), which produces:    Hmm, must be some subtle syntax thing:   : [tag:failure](https://superuser.com/questions/tagged/failure) []: [[tag:failure](https://superuser.com/questions/tagged/failure)] : [tag:[failure]((https://superuser.com/questions/tagged/failure))] : &lt;a href="https://superuser.com/questions/tagged/failure"&gt;[tag:failure]&lt;/a&gt; : [tag:failure][1] \n\n [1]: https://superuser.com/questions/tagged/failure : [more text is a [tag:failure] too](https://superuser.com/questions/tagged/failure)   I give up!  How can I create a link to a tag on another site with tag markdown?