# Email server, where is the bottleneck?



## libro22 (May 17, 2017)

If I'm to put up a server dedicated for emails (currently being used for IMAP and Roundcube), which bottleneck should I focus on? Is it CPU or memory? I'm thinking of getting a VPS first (both companies I'm checking out have SSDs, so I don't think I/O should be an issue). They just differ with Dedicated CPU vs Shared, and Higher vs Lower memory.


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## CenTex Hosting (May 17, 2017)

How many Emails are you talking about sending? If you are just sending normal use then no worries about bottleneck. Now if you are trying to send millions of emails at a time. There there are a few things to look at. first would be the host and do they allow mass mailing, 2 what is the mail rate limit per hour they have set.


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## libro22 (May 17, 2017)

My current server is actually sending about 10k emails a month, valid transactional and regular emails. Active domain senders are around 10 with less than 10 active accounts each.

I dont mind deliverability as I'm using mailchannels. Though I currently have local anti-spam processes and thinking of offloading this to a 3rd party anti spam.

Current server is getting loads of 4-5 out of 16 CPUs (Dedicated Server) on regular work hours as active IMAP and roundcube processes are filling it up. This is what I'm concerned of if I move them to VPS with hopes of future expansion.


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## Nick (May 18, 2017)

With those kinds of loads you may get away with having a VPS. Are those loads only during peak hours and if so, for how long? What's the server that you currently have?


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## libro22 (May 18, 2017)

A pretty old L5520 

Yep, I pretty much guessed that VPS would suffice. But I still don't know which resource IMAP and Roundcube use the most, is it CPU or memory? And where it would benefit more.
I can't base it on my usage as my disks are pretty slow (and old)


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## fm7 (May 18, 2017)

libro22 said:


> Current server is getting loads of 4-5 out of 16 CPUs (Dedicated Server) on regular work hours as active IMAP and roundcube processes are filling it up. This is what I'm concerned of if I move them to VPS with hopes of future expansion.



8 cores with hyperthreading ~10 "CPUs" and load 5 usually implies 5 cores 100% in use. You are using a lot of processing power that I guess VPS providers probably won't be happy to sustain. I suggest you to use PERF to learn about your actual requirement -- "load" is crapware.


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## libro22 (May 18, 2017)

I've checked my stats and my disks are the culprit for this, util is around 60-90 that's why I can't compare it on my end. It's also a cPanel server, performance is mixed. CPU utilization is actually on the low part why memory is more on MySQL.


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## Jonathan (May 18, 2017)

If you have a lot of IMAP boxes don't forget about disk I/O. Do you have hundreds of thousands of emails between all of the IMAP accounts?

Regardless, email is always a good place to throw in an SSD.


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## libro22 (May 18, 2017)

No, just a few thousands < 10k per mailbox, averages 2k maybe.

Yep, I'm now considering that it's more of an I/O issue rather than CPU or memory, will figure out which provider is best for me.


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## norival1992 (Jul 20, 2017)

There's a chance your email could be slow due to warming-up new IPs, ISP spam filters, or how your delivery throttling rules are configured


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